Generate CustomFeatureFlags

* Creates a new general-purpose CustomFeatureFlags class
* Simplifies FakeFeatureFlagsImpl to be based on that
* This allows teams to fake FeatureFlags without having to make changes per flag.
* This allows SetFlagsRule to inject an instance of FeatureFlags that would detect if a flag has been read.

Bug: 336768870
Flag: none
Test: presubmit
Change-Id: Id3c2530d484fa5584c46d11381fcfc0ab294f33f

NOTE FOR REVIEWERS - original patch and result patch are not identical.
PLEASE REVIEW CAREFULLY.
Diffs between the patches:
     "CustomFeatureFlags.java",
> +        include_str!("../../templates/CustomFeatureFlags.java.template"),
> +    )?;
> +    template.add_template(
> -    ["Flags.java", "FeatureFlags.java", "FeatureFlagsImpl.java", "FakeFeatureFlagsImpl.java"]
> -        .iter()
> -        .map(|file| {
> -            Ok(OutputFile {
> -                contents: template.render(file, &context)?.into(),
> -                path: path.join(file),
> -            })
> -        })
> -        .collect::<Result<Vec<OutputFile>>>()
> +    [
> +        "Flags.java",
> +        "FeatureFlags.java",
> +        "FeatureFlagsImpl.java",
> +        "CustomFeatureFlags.java",
> +        "FakeFeatureFlagsImpl.java",
> +    ]
> +    .iter()
> +    .map(|file| {
> +        Ok(OutputFile { contents: template.render(file, &context)?.into(), path: path.join(file) })
> +    })
> +    .collect::<Result<Vec<OutputFile>>>()
> -    const EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT: &str = r#"
> +    const EXPECTED_CUSTOMFEATUREFLAGS_CONTENT: &str = r#"
> +
> -    import java.util.HashMap;
> -    import java.util.Map;
> +    import java.util.List;
> +    import java.util.function.BiPredicate;
> +    import java.util.function.Predicate;
> +
> -    public class FakeFeatureFlagsImpl implements FeatureFlags {
> -        public FakeFeatureFlagsImpl() {
> -            resetAll();
> +    public class CustomFeatureFlags implements FeatureFlags {
> +
> +        private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
> +
> +        public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) {
> +            mGetValueImpl = getValueImpl;
> +
> -            return getValue(Flags.FLAG_DISABLED_RO);
> +            return getValue(Flags.FLAG_DISABLED_RO,
> +                    FeatureFlags::disabledRo);
> -            return getValue(Flags.FLAG_DISABLED_RW);
> +            return getValue(Flags.FLAG_DISABLED_RW,
> +                FeatureFlags::disabledRw);
> -            return getValue(Flags.FLAG_DISABLED_RW_EXPORTED);
> +            return getValue(Flags.FLAG_DISABLED_RW_EXPORTED,
> +                FeatureFlags::disabledRwExported);
> -            return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE);
> +            return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
> +                FeatureFlags::disabledRwInOtherNamespace);
> -            return getValue(Flags.FLAG_ENABLED_FIXED_RO);
> +            return getValue(Flags.FLAG_ENABLED_FIXED_RO,
> +                FeatureFlags::enabledFixedRo);
> -            return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED);
> +            return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
> +                FeatureFlags::enabledFixedRoExported);
> -            return getValue(Flags.FLAG_ENABLED_RO);
> +            return getValue(Flags.FLAG_ENABLED_RO,
> +                FeatureFlags::enabledRo);
> -            return getValue(Flags.FLAG_ENABLED_RO_EXPORTED);
> +            return getValue(Flags.FLAG_ENABLED_RO_EXPORTED,
> +                FeatureFlags::enabledRoExported);
> -            return getValue(Flags.FLAG_ENABLED_RW);
> +            return getValue(Flags.FLAG_ENABLED_RW,
> +                FeatureFlags::enabledRw);
> -        public void setFlag(String flagName, boolean value) {
> -            if (!this.mFlagMap.containsKey(flagName)) {
> -                throw new IllegalArgumentException("no such flag " + flagName);
> -            }
> -            this.mFlagMap.put(flagName, value);
> -        }
> -        public void resetAll() {
> -            for (Map.Entry entry : mFlagMap.entrySet()) {
> -                entry.setValue(null);
> -            }
> -        }
> +
> +
> -        private boolean getValue(String flagName) {
> -            Boolean value = this.mFlagMap.get(flagName);
> -            if (value == null) {
> -                throw new IllegalArgumentException(flagName + " is not set");
> -            }
> -            return value;
> +
> +        protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
> +            return mGetValueImpl.test(flagName, getter);
> -        private Map<String, Boolean> mFlagMap = new HashMap<>(
> -            Map.ofEntries(
> -                Map.entry(Flags.FLAG_DISABLED_RO, false),
> -                Map.entry(Flags.FLAG_DISABLED_RW, false),
> -                Map.entry(Flags.FLAG_DISABLED_RW_EXPORTED, false),
> -                Map.entry(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE, false),
> -                Map.entry(Flags.FLAG_ENABLED_FIXED_RO, false),
> -                Map.entry(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED, false),
> -                Map.entry(Flags.FLAG_ENABLED_RO, false),
> -                Map.entry(Flags.FLAG_ENABLED_RO_EXPORTED, false),
> -                Map.entry(Flags.FLAG_ENABLED_RW, false)
> -            )
> -        );
> +
> +        public List<String> getFlagNames() {
> +            return Arrays.asList(
> +                Flags.FLAG_DISABLED_RO,
> +                Flags.FLAG_DISABLED_RW,
> +                Flags.FLAG_DISABLED_RW_EXPORTED,
> +                Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
> +                Flags.FLAG_ENABLED_FIXED_RO,
> +                Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
> +                Flags.FLAG_ENABLED_RO,
> +                Flags.FLAG_ENABLED_RO_EXPORTED,
> +                Flags.FLAG_ENABLED_RW
> +            );
> +        }
> +
> +    const EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT: &str = r#"
> +    package com.android.aconfig.test;
> +
> +    import java.util.HashMap;
> +    import java.util.Map;
> +    import java.util.function.Predicate;
> +
> +    /** @hide */
> +    public class FakeFeatureFlagsImpl extends CustomFeatureFlags {
> +        private Map<String, Boolean> mFlagMap = new HashMap<>();
> +
> +        public FakeFeatureFlagsImpl() {
> +            super(null);
> +            // Initialize the map with null values
> +            for (String flagName : getFlagNames()) {
> +                mFlagMap.put(flagName, null);
> +            }
> +        }
> +
> +        @Override
> +        protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
> +            Boolean value = this.mFlagMap.get(flagName);
> +            if (value == null) {
> +                throw new IllegalArgumentException(flagName + " is not set");
> +            }
> +            return value;
> +        }
> +
> +        public void setFlag(String flagName, boolean value) {
> +            if (!this.mFlagMap.containsKey(flagName)) {
> +                throw new IllegalArgumentException("no such flag " + flagName);
> +            }
> +            this.mFlagMap.put(flagName, value);
> +        }
> +
> +        public void resetAll() {
> +            for (Map.Entry entry : mFlagMap.entrySet()) {
> +                entry.setValue(null);
> +            }
> +        }
> +    }
> +    "#;
> +
> +                "com/android/aconfig/test/CustomFeatureFlags.java",
> +                EXPECTED_CUSTOMFEATUREFLAGS_CONTENT,
> +            ),
> +            (
> -        let expect_fake_feature_flags_impl_content = r#"
> +        let expect_custom_feature_flags_content = r#"
> +
> -        import java.util.HashMap;
> -        import java.util.Map;
> +        import java.util.List;
> +        import java.util.function.BiPredicate;
> +        import java.util.function.Predicate;
> +
> -        public class FakeFeatureFlagsImpl implements FeatureFlags {
> -            public FakeFeatureFlagsImpl() {
> -                resetAll();
> +        public class CustomFeatureFlags implements FeatureFlags {
> +
> +            private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
> +
> +            public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) {
> +                mGetValueImpl = getValueImpl;
> +
> -                return getValue(Flags.FLAG_DISABLED_RW_EXPORTED);
> +                return getValue(Flags.FLAG_DISABLED_RW_EXPORTED,
> +                    FeatureFlags::disabledRwExported);
> -                return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED);
> +                return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
> +                    FeatureFlags::enabledFixedRoExported);
> -                return getValue(Flags.FLAG_ENABLED_RO_EXPORTED);
> +                return getValue(Flags.FLAG_ENABLED_RO_EXPORTED,
> +                    FeatureFlags::enabledRoExported);
> -            public void setFlag(String flagName, boolean value) {
> -                if (!this.mFlagMap.containsKey(flagName)) {
> -                    throw new IllegalArgumentException("no such flag " + flagName);
> -                }
> -                this.mFlagMap.put(flagName, value);
> +
> +            protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
> +                return mGetValueImpl.test(flagName, getter);
> -            public void resetAll() {
> -                for (Map.Entry entry : mFlagMap.entrySet()) {
> -                    entry.setValue(null);
> -                }
> +
> +            public List<String> getFlagNames() {
> +                return Arrays.asList(
> +                    Flags.FLAG_DISABLED_RW_EXPORTED,
> +                    Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
> +                    Flags.FLAG_ENABLED_RO_EXPORTED
> +                );
> -            private boolean getValue(String flagName) {
> -                Boolean value = this.mFlagMap.get(flagName);
> -                if (value == null) {
> -                    throw new IllegalArgumentException(flagName + " is not set");
> -                }
> -                return value;
> -            }
> -            private Map<String, Boolean> mFlagMap = new HashMap<>(
> -                Map.ofEntries(
> -                    Map.entry(Flags.FLAG_DISABLED_RW_EXPORTED, false),
> -                    Map.entry(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED, false),
> -                    Map.entry(Flags.FLAG_ENABLED_RO_EXPORTED, false)
> -                )
> -            );
> +
> +                "com/android/aconfig/test/CustomFeatureFlags.java",
> +                expect_custom_feature_flags_content,
> +            ),
> +            (
> -                expect_fake_feature_flags_impl_content,
> +                EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
> +                "com/android/aconfig/test/CustomFeatureFlags.java",
> +                EXPECTED_CUSTOMFEATUREFLAGS_CONTENT,
> +            ),
> +            (
> -        let expect_fakefeatureflags_content = r#"
> +        let expect_customfeatureflags_content = r#"
> +
> -        import java.util.HashMap;
> -        import java.util.Map;
> +        import java.util.List;
> +        import java.util.function.BiPredicate;
> +        import java.util.function.Predicate;
> +
> -        public class FakeFeatureFlagsImpl implements FeatureFlags {
> -            public FakeFeatureFlagsImpl() {
> -                resetAll();
> +        public class CustomFeatureFlags implements FeatureFlags {
> +
> +            private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
> +
> +            public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) {
> +                mGetValueImpl = getValueImpl;
> +
> -                return getValue(Flags.FLAG_DISABLED_RO);
> +                return getValue(Flags.FLAG_DISABLED_RO,
> +                        FeatureFlags::disabledRo);
> -                return getValue(Flags.FLAG_DISABLED_RW);
> +                return getValue(Flags.FLAG_DISABLED_RW,
> +                    FeatureFlags::disabledRw);
> -                return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE);
> +                return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
> +                    FeatureFlags::disabledRwInOtherNamespace);
> -                return getValue(Flags.FLAG_ENABLED_FIXED_RO);
> +                return getValue(Flags.FLAG_ENABLED_FIXED_RO,
> +                    FeatureFlags::enabledFixedRo);
> -                return getValue(Flags.FLAG_ENABLED_RO);
> +                return getValue(Flags.FLAG_ENABLED_RO,
> +                    FeatureFlags::enabledRo);
> -                return getValue(Flags.FLAG_ENABLED_RW);
> +                return getValue(Flags.FLAG_ENABLED_RW,
> +                    FeatureFlags::enabledRw);
> -            public void setFlag(String flagName, boolean value) {
> -                if (!this.mFlagMap.containsKey(flagName)) {
> -                    throw new IllegalArgumentException("no such flag " + flagName);
> -                }
> -                this.mFlagMap.put(flagName, value);
> -            }
> -            public void resetAll() {
> -                for (Map.Entry entry : mFlagMap.entrySet()) {
> -                    entry.setValue(null);
> -                }
> -            }
> +
> +
> -            private boolean getValue(String flagName) {
> -                Boolean value = this.mFlagMap.get(flagName);
> -                if (value == null) {
> -                    throw new IllegalArgumentException(flagName + " is not set");
> -                }
> -                return value;
> +
> +            protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
> +                return mGetValueImpl.test(flagName, getter);
> -            private Map<String, Boolean> mFlagMap = new HashMap<>(
> -                Map.ofEntries(
> -                    Map.entry(Flags.FLAG_DISABLED_RO, false),
> -                    Map.entry(Flags.FLAG_DISABLED_RW, false),
> -                    Map.entry(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE, false),
> -                    Map.entry(Flags.FLAG_ENABLED_FIXED_RO, false),
> -                    Map.entry(Flags.FLAG_ENABLED_RO, false),
> -                    Map.entry(Flags.FLAG_ENABLED_RW, false)
> -                )
> -            );
> +
> +            public List<String> getFlagNames() {
> +                return Arrays.asList(
> +                    Flags.FLAG_DISABLED_RO,
> +                    Flags.FLAG_DISABLED_RW,
> +                    Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
> +                    Flags.FLAG_ENABLED_FIXED_RO,
> +                    Flags.FLAG_ENABLED_RO,
> +                    Flags.FLAG_ENABLED_RW
> +                );
> +            }
> +
> +
> -            ("com/android/aconfig/test/FakeFeatureFlagsImpl.java", expect_fakefeatureflags_content),
> +            ("com/android/aconfig/test/CustomFeatureFlags.java", expect_customfeatureflags_content),
> +            (
> +                "com/android/aconfig/test/FakeFeatureFlagsImpl.java",
> +                EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
> +            ),
> --- /dev/null
> +++ tools/aconfig/aconfig/templates/CustomFeatureFlags.java.template
> +package {package_name};
> +
> +{{ if not library_exported- }}
> +// TODO(b/303773055): Remove the annotation after access issue is resolved.
> +import android.compat.annotation.UnsupportedAppUsage;
> +{{ -endif }}
> +import java.util.Arrays;
> +import java.util.HashSet;
> +import java.util.List;
> +import java.util.Set;
> +import java.util.function.BiPredicate;
> +import java.util.function.Predicate;
> +
> +/** @hide */
> +public class CustomFeatureFlags implements FeatureFlags \{
> +
> +    private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
> +
> +    public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) \{
> +        mGetValueImpl = getValueImpl;
> +    }
> +
> +{{ -for item in flag_elements}}
> +    @Override
> +{{ if not library_exported }}    @UnsupportedAppUsage{{ -endif }}
> +    public boolean {item.method_name}() \{
> +        return getValue(Flags.FLAG_{item.flag_name_constant_suffix},
> +            FeatureFlags::{item.method_name});
> +    }
> +{{ endfor }}
> +
> +{{ -if not library_exported }}
> +    public boolean isFlagReadOnlyOptimized(String flagName) \{
> +        if (mReadOnlyFlagsSet.contains(flagName) &&
> +            isOptimizationEnabled()) \{
> +                return true;
> +        }
> +        return false;
> +    }
> +
> +    @com.android.aconfig.annotations.AssumeTrueForR8
> +    private boolean isOptimizationEnabled() \{
> +        return false;
> +    }
> +{{ -endif }}
> +
> +    protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) \{
> +        return mGetValueImpl.test(flagName, getter);
> +    }
> +
> +    public List<String> getFlagNames() \{
> +        return Arrays.asList(
> +            {{ -for item in flag_elements }}
> +            Flags.FLAG_{item.flag_name_constant_suffix}
> +            {{ -if not @last }},{{ endif }}
> +            {{ -endfor }}
> +        );
> +    }
> +
> +    private Set<String> mReadOnlyFlagsSet = new HashSet<>(
> +        Arrays.asList(
> +            {{ -for item in flag_elements }}
> +            {{ -if not item.is_read_write }}
> +            Flags.FLAG_{item.flag_name_constant_suffix},
> +            {{ -endif }}
> +            {{ -endfor }}
> +            ""{# The empty string here is to resolve the ending comma #}
> +        )
> +    );
> +}
> --- tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template
> +++ tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template
> -{{ if not library_exported- }}
> -// TODO(b/303773055): Remove the annotation after access issue is resolved.
> -import android.compat.annotation.UnsupportedAppUsage;
> -{{ -endif }}
> -import java.util.Arrays;
> +
> -import java.util.HashSet;
> -import java.util.Set;
> +import java.util.function.Predicate;
> -public class FakeFeatureFlagsImpl implements FeatureFlags \{
> +public class FakeFeatureFlagsImpl extends CustomFeatureFlags \{
> +    private Map<String, Boolean> mFlagMap = new HashMap<>();
> +
> -        resetAll();
> +        super(null);
> +        // Initialize the map with null values
> +        for (String flagName : getFlagNames()) \{
> +            mFlagMap.put(flagName, null);
> +        }
> -{{ for item in flag_elements}}
> -{{ if not library_exported }}    @UnsupportedAppUsage{{ -endif }}
> -    public boolean {item.method_name}() \{
> -        return getValue(Flags.FLAG_{item.flag_name_constant_suffix});
> +    protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) \{
> +        Boolean value = this.mFlagMap.get(flagName);
> +        if (value == null) \{
> +            throw new IllegalArgumentException(flagName + " is not set");
> +        }
> +        return value;
> -{{ endfor}}
> +
> -{{ if not library_exported }}
> -    public boolean isFlagReadOnlyOptimized(String flagName) \{
> -        if (mReadOnlyFlagsSet.contains(flagName) &&
> -            isOptimizationEnabled()) \{
> -                return true;
> -        }
> -        return false;
> -    }
> -
> -    @com.android.aconfig.annotations.AssumeTrueForR8
> -    private boolean isOptimizationEnabled() \{
> -        return false;
> -    }
> -{{ -endif }}
> -    private boolean getValue(String flagName) \{
> -        Boolean value = this.mFlagMap.get(flagName);
> -        if (value == null) \{
> -            throw new IllegalArgumentException(flagName + " is not set");
> -        }
> -        return value;
> -    }
> -
> -
> -    private Map<String, Boolean> mFlagMap = new HashMap<>(
> -        Map.ofEntries(
> -            {{ -for item in flag_elements }}
> -            Map.entry(Flags.FLAG_{item.flag_name_constant_suffix}, false)
> -            {{ -if not @last }},{{ endif }}
> -            {{ -endfor }}
> -        )
> -    );
> -
> -    private Set<String> mReadOnlyFlagsSet = new HashSet<>(
> -        Arrays.asList(
> -            {{ -for item in flag_elements }}
> -            {{ -if not item.is_read_write }}
> -            Flags.FLAG_{item.flag_name_constant_suffix},
> -            {{ -endif }}
> -            {{ -endfor }}
> -            ""{# The empty string here is to resolve the ending comma #}
> -        )
> -    );

Original patch:
 diff --git a/tools/aconfig/aconfig/src/codegen/java.rs b/tools/aconfig/aconfig/src/codegen/java.rs
old mode 100644
new mode 100644
--- a/tools/aconfig/aconfig/src/codegen/java.rs
+++ b/tools/aconfig/aconfig/src/codegen/java.rs
@@ -63,21 +63,28 @@
         "FeatureFlags.java",
         include_str!("../../templates/FeatureFlags.java.template"),
     )?;
+    template.add_template(
+        "CustomFeatureFlags.java",
+        include_str!("../../templates/CustomFeatureFlags.java.template"),
+    )?;
     template.add_template(
         "FakeFeatureFlagsImpl.java",
         include_str!("../../templates/FakeFeatureFlagsImpl.java.template"),
     )?;
 
     let path: PathBuf = package.split('.').collect();
-    ["Flags.java", "FeatureFlags.java", "FeatureFlagsImpl.java", "FakeFeatureFlagsImpl.java"]
-        .iter()
-        .map(|file| {
-            Ok(OutputFile {
-                contents: template.render(file, &context)?.into(),
-                path: path.join(file),
-            })
-        })
-        .co
[[[Original patch trimmed due to size. Decoded string size: 26318. Decoded string SHA1: 7db34b7baf0a0bbaa1cff48b6ccab9c65408e743.]]]

Result patch:
 diff --git a/tools/aconfig/aconfig/src/codegen/java.rs b/tools/aconfig/aconfig/src/codegen/java.rs
index 18a4be5..9abc892 100644
--- a/tools/aconfig/aconfig/src/codegen/java.rs
+++ b/tools/aconfig/aconfig/src/codegen/java.rs
@@ -64,20 +64,27 @@
         include_str!("../../templates/FeatureFlags.java.template"),
     )?;
     template.add_template(
+        "CustomFeatureFlags.java",
+        include_str!("../../templates/CustomFeatureFlags.java.template"),
+    )?;
+    template.add_template(
         "FakeFeatureFlagsImpl.java",
         include_str!("../../templates/FakeFeatureFlagsImpl.java.template"),
     )?;
 
     let path: PathBuf = package.split('.').collect();
-    ["Flags.java", "FeatureFlags.java", "FeatureFlagsImpl.java", "FakeFeatureFlagsImpl.java"]
-        .iter()
-        .map(|file| {
-            Ok(OutputFile {
-                contents: template.render(file, &context)?.into(),
-                path: path.join(file),
-            })
-        })
-        .collect::<Result<Vec<OutputFile>>>
[[[Result patch trimmed due to size. Decoded string size: 26308. Decoded string SHA1: bb07ee948a630a6bc4cfbbf2a8df178f3e6d3103.]]]

Change-Id: I94184633303b9d76f7943451fb3b2c93d071ec1c

3 files changed, 289 insertions, 184 deletions

diff --git a/tools/aconfig/aconfig/src/codegen/java.rs b/tools/aconfig/aconfig/src/codegen/java.rs
index 18a4be5094..9abc892908 100644
--- a/tools/aconfig/aconfig/src/codegen/java.rs
+++ b/tools/aconfig/aconfig/src/codegen/java.rs
@@ -64,20 +64,27 @@ where
         include_str!("../../templates/FeatureFlags.java.template"),
     )?;
     template.add_template(
+        "CustomFeatureFlags.java",
+        include_str!("../../templates/CustomFeatureFlags.java.template"),
+    )?;
+    template.add_template(
         "FakeFeatureFlagsImpl.java",
         include_str!("../../templates/FakeFeatureFlagsImpl.java.template"),
     )?;
 
     let path: PathBuf = package.split('.').collect();
-    ["Flags.java", "FeatureFlags.java", "FeatureFlagsImpl.java", "FakeFeatureFlagsImpl.java"]
-        .iter()
-        .map(|file| {
-            Ok(OutputFile {
-                contents: template.render(file, &context)?.into(),
-                path: path.join(file),
-            })
-        })
-        .collect::<Result<Vec<OutputFile>>>()
+    [
+        "Flags.java",
+        "FeatureFlags.java",
+        "FeatureFlagsImpl.java",
+        "CustomFeatureFlags.java",
+        "FakeFeatureFlagsImpl.java",
+    ]
+    .iter()
+    .map(|file| {
+        Ok(OutputFile { contents: template.render(file, &context)?.into(), path: path.join(file) })
+    })
+    .collect::<Result<Vec<OutputFile>>>()
 }
 
 fn gen_flags_by_namespace(flags: &[FlagElement]) -> Vec<NamespaceFlags> {
@@ -292,76 +299,82 @@ mod tests {
         }
     "#;
 
-    const EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT: &str = r#"
+    const EXPECTED_CUSTOMFEATUREFLAGS_CONTENT: &str = r#"
     package com.android.aconfig.test;
+
     // TODO(b/303773055): Remove the annotation after access issue is resolved.
     import android.compat.annotation.UnsupportedAppUsage;
     import java.util.Arrays;
-    import java.util.HashMap;
     import java.util.HashSet;
-    import java.util.Map;
+    import java.util.List;
     import java.util.Set;
+    import java.util.function.BiPredicate;
+    import java.util.function.Predicate;
+
     /** @hide */
-    public class FakeFeatureFlagsImpl implements FeatureFlags {
-        public FakeFeatureFlagsImpl() {
-            resetAll();
+    public class CustomFeatureFlags implements FeatureFlags {
+
+        private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
+
+        public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) {
+            mGetValueImpl = getValueImpl;
         }
+
         @Override
         @UnsupportedAppUsage
         public boolean disabledRo() {
-            return getValue(Flags.FLAG_DISABLED_RO);
+            return getValue(Flags.FLAG_DISABLED_RO,
+                    FeatureFlags::disabledRo);
         }
         @Override
         @UnsupportedAppUsage
         public boolean disabledRw() {
-            return getValue(Flags.FLAG_DISABLED_RW);
+            return getValue(Flags.FLAG_DISABLED_RW,
+                FeatureFlags::disabledRw);
         }
         @Override
         @UnsupportedAppUsage
         public boolean disabledRwExported() {
-            return getValue(Flags.FLAG_DISABLED_RW_EXPORTED);
+            return getValue(Flags.FLAG_DISABLED_RW_EXPORTED,
+                FeatureFlags::disabledRwExported);
         }
         @Override
         @UnsupportedAppUsage
         public boolean disabledRwInOtherNamespace() {
-            return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE);
+            return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
+                FeatureFlags::disabledRwInOtherNamespace);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledFixedRo() {
-            return getValue(Flags.FLAG_ENABLED_FIXED_RO);
+            return getValue(Flags.FLAG_ENABLED_FIXED_RO,
+                FeatureFlags::enabledFixedRo);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledFixedRoExported() {
-            return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED);
+            return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
+                FeatureFlags::enabledFixedRoExported);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledRo() {
-            return getValue(Flags.FLAG_ENABLED_RO);
+            return getValue(Flags.FLAG_ENABLED_RO,
+                FeatureFlags::enabledRo);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledRoExported() {
-            return getValue(Flags.FLAG_ENABLED_RO_EXPORTED);
+            return getValue(Flags.FLAG_ENABLED_RO_EXPORTED,
+                FeatureFlags::enabledRoExported);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledRw() {
-            return getValue(Flags.FLAG_ENABLED_RW);
-        }
-        public void setFlag(String flagName, boolean value) {
-            if (!this.mFlagMap.containsKey(flagName)) {
-                throw new IllegalArgumentException("no such flag " + flagName);
-            }
-            this.mFlagMap.put(flagName, value);
-        }
-        public void resetAll() {
-            for (Map.Entry entry : mFlagMap.entrySet()) {
-                entry.setValue(null);
-            }
+            return getValue(Flags.FLAG_ENABLED_RW,
+                FeatureFlags::enabledRw);
         }
+
         public boolean isFlagReadOnlyOptimized(String flagName) {
             if (mReadOnlyFlagsSet.contains(flagName) &&
                 isOptimizationEnabled()) {
@@ -369,30 +382,30 @@ mod tests {
             }
             return false;
         }
+
         @com.android.aconfig.annotations.AssumeTrueForR8
         private boolean isOptimizationEnabled() {
             return false;
         }
-        private boolean getValue(String flagName) {
-            Boolean value = this.mFlagMap.get(flagName);
-            if (value == null) {
-                throw new IllegalArgumentException(flagName + " is not set");
-            }
-            return value;
+
+        protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
+            return mGetValueImpl.test(flagName, getter);
         }
-        private Map<String, Boolean> mFlagMap = new HashMap<>(
-            Map.ofEntries(
-                Map.entry(Flags.FLAG_DISABLED_RO, false),
-                Map.entry(Flags.FLAG_DISABLED_RW, false),
-                Map.entry(Flags.FLAG_DISABLED_RW_EXPORTED, false),
-                Map.entry(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE, false),
-                Map.entry(Flags.FLAG_ENABLED_FIXED_RO, false),
-                Map.entry(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED, false),
-                Map.entry(Flags.FLAG_ENABLED_RO, false),
-                Map.entry(Flags.FLAG_ENABLED_RO_EXPORTED, false),
-                Map.entry(Flags.FLAG_ENABLED_RW, false)
-            )
-        );
+
+        public List<String> getFlagNames() {
+            return Arrays.asList(
+                Flags.FLAG_DISABLED_RO,
+                Flags.FLAG_DISABLED_RW,
+                Flags.FLAG_DISABLED_RW_EXPORTED,
+                Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
+                Flags.FLAG_ENABLED_FIXED_RO,
+                Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
+                Flags.FLAG_ENABLED_RO,
+                Flags.FLAG_ENABLED_RO_EXPORTED,
+                Flags.FLAG_ENABLED_RW
+            );
+        }
+
         private Set<String> mReadOnlyFlagsSet = new HashSet<>(
             Arrays.asList(
                 Flags.FLAG_DISABLED_RO,
@@ -406,6 +419,49 @@ mod tests {
     }
     "#;
 
+    const EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT: &str = r#"
+    package com.android.aconfig.test;
+
+    import java.util.HashMap;
+    import java.util.Map;
+    import java.util.function.Predicate;
+
+    /** @hide */
+    public class FakeFeatureFlagsImpl extends CustomFeatureFlags {
+        private Map<String, Boolean> mFlagMap = new HashMap<>();
+
+        public FakeFeatureFlagsImpl() {
+            super(null);
+            // Initialize the map with null values
+            for (String flagName : getFlagNames()) {
+                mFlagMap.put(flagName, null);
+            }
+        }
+
+        @Override
+        protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
+            Boolean value = this.mFlagMap.get(flagName);
+            if (value == null) {
+                throw new IllegalArgumentException(flagName + " is not set");
+            }
+            return value;
+        }
+
+        public void setFlag(String flagName, boolean value) {
+            if (!this.mFlagMap.containsKey(flagName)) {
+                throw new IllegalArgumentException("no such flag " + flagName);
+            }
+            this.mFlagMap.put(flagName, value);
+        }
+
+        public void resetAll() {
+            for (Map.Entry entry : mFlagMap.entrySet()) {
+                entry.setValue(null);
+            }
+        }
+    }
+    "#;
+
     #[test]
     fn test_generate_java_code_production() {
         let parsed_flags = crate::test::parse_test_flags();
@@ -549,6 +605,10 @@ mod tests {
             ("com/android/aconfig/test/FeatureFlagsImpl.java", expect_featureflagsimpl_content),
             ("com/android/aconfig/test/FeatureFlags.java", EXPECTED_FEATUREFLAGS_COMMON_CONTENT),
             (
+                "com/android/aconfig/test/CustomFeatureFlags.java",
+                EXPECTED_CUSTOMFEATUREFLAGS_CONTENT,
+            ),
+            (
                 "com/android/aconfig/test/FakeFeatureFlagsImpl.java",
                 EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
             ),
@@ -671,55 +731,53 @@ mod tests {
             }
         }"#;
 
-        let expect_fake_feature_flags_impl_content = r#"
+        let expect_custom_feature_flags_content = r#"
         package com.android.aconfig.test;
+
         import java.util.Arrays;
-        import java.util.HashMap;
         import java.util.HashSet;
-        import java.util.Map;
+        import java.util.List;
         import java.util.Set;
+        import java.util.function.BiPredicate;
+        import java.util.function.Predicate;
+
         /** @hide */
-        public class FakeFeatureFlagsImpl implements FeatureFlags {
-            public FakeFeatureFlagsImpl() {
-                resetAll();
+        public class CustomFeatureFlags implements FeatureFlags {
+
+            private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
+
+            public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) {
+                mGetValueImpl = getValueImpl;
             }
+
             @Override
             public boolean disabledRwExported() {
-                return getValue(Flags.FLAG_DISABLED_RW_EXPORTED);
+                return getValue(Flags.FLAG_DISABLED_RW_EXPORTED,
+                    FeatureFlags::disabledRwExported);
             }
             @Override
             public boolean enabledFixedRoExported() {
-                return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED);
+                return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
+                    FeatureFlags::enabledFixedRoExported);
             }
             @Override
             public boolean enabledRoExported() {
-                return getValue(Flags.FLAG_ENABLED_RO_EXPORTED);
-            }
-            public void setFlag(String flagName, boolean value) {
-                if (!this.mFlagMap.containsKey(flagName)) {
-                    throw new IllegalArgumentException("no such flag " + flagName);
-                }
-                this.mFlagMap.put(flagName, value);
+                return getValue(Flags.FLAG_ENABLED_RO_EXPORTED,
+                    FeatureFlags::enabledRoExported);
             }
-            public void resetAll() {
-                for (Map.Entry entry : mFlagMap.entrySet()) {
-                    entry.setValue(null);
-                }
+
+            protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
+                return mGetValueImpl.test(flagName, getter);
             }
-            private boolean getValue(String flagName) {
-                Boolean value = this.mFlagMap.get(flagName);
-                if (value == null) {
-                    throw new IllegalArgumentException(flagName + " is not set");
-                }
-                return value;
+
+            public List<String> getFlagNames() {
+                return Arrays.asList(
+                    Flags.FLAG_DISABLED_RW_EXPORTED,
+                    Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
+                    Flags.FLAG_ENABLED_RO_EXPORTED
+                );
             }
-            private Map<String, Boolean> mFlagMap = new HashMap<>(
-                Map.ofEntries(
-                    Map.entry(Flags.FLAG_DISABLED_RW_EXPORTED, false),
-                    Map.entry(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED, false),
-                    Map.entry(Flags.FLAG_ENABLED_RO_EXPORTED, false)
-                )
-            );
+
             private Set<String> mReadOnlyFlagsSet = new HashSet<>(
                 Arrays.asList(
                     ""
@@ -733,8 +791,12 @@ mod tests {
             ("com/android/aconfig/test/FeatureFlags.java", expect_feature_flags_content),
             ("com/android/aconfig/test/FeatureFlagsImpl.java", expect_feature_flags_impl_content),
             (
+                "com/android/aconfig/test/CustomFeatureFlags.java",
+                expect_custom_feature_flags_content,
+            ),
+            (
                 "com/android/aconfig/test/FakeFeatureFlagsImpl.java",
-                expect_fake_feature_flags_impl_content,
+                EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
             ),
         ]);
 
@@ -854,6 +916,10 @@ mod tests {
             ("com/android/aconfig/test/FeatureFlags.java", EXPECTED_FEATUREFLAGS_COMMON_CONTENT),
             ("com/android/aconfig/test/FeatureFlagsImpl.java", expect_featureflagsimpl_content),
             (
+                "com/android/aconfig/test/CustomFeatureFlags.java",
+                EXPECTED_CUSTOMFEATUREFLAGS_CONTENT,
+            ),
+            (
                 "com/android/aconfig/test/FakeFeatureFlagsImpl.java",
                 EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
             ),
@@ -1020,61 +1086,64 @@ mod tests {
             private static FeatureFlags FEATURE_FLAGS = new FeatureFlagsImpl();
         }"#;
 
-        let expect_fakefeatureflags_content = r#"
+        let expect_customfeatureflags_content = r#"
         package com.android.aconfig.test;
+
         // TODO(b/303773055): Remove the annotation after access issue is resolved.
         import android.compat.annotation.UnsupportedAppUsage;
         import java.util.Arrays;
-        import java.util.HashMap;
         import java.util.HashSet;
-        import java.util.Map;
+        import java.util.List;
         import java.util.Set;
+        import java.util.function.BiPredicate;
+        import java.util.function.Predicate;
+
         /** @hide */
-        public class FakeFeatureFlagsImpl implements FeatureFlags {
-            public FakeFeatureFlagsImpl() {
-                resetAll();
+        public class CustomFeatureFlags implements FeatureFlags {
+
+            private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
+
+            public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) {
+                mGetValueImpl = getValueImpl;
             }
+
             @Override
             @UnsupportedAppUsage
             public boolean disabledRo() {
-                return getValue(Flags.FLAG_DISABLED_RO);
+                return getValue(Flags.FLAG_DISABLED_RO,
+                        FeatureFlags::disabledRo);
             }
             @Override
             @UnsupportedAppUsage
             public boolean disabledRw() {
-                return getValue(Flags.FLAG_DISABLED_RW);
+                return getValue(Flags.FLAG_DISABLED_RW,
+                    FeatureFlags::disabledRw);
             }
             @Override
             @UnsupportedAppUsage
             public boolean disabledRwInOtherNamespace() {
-                return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE);
+                return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
+                    FeatureFlags::disabledRwInOtherNamespace);
             }
             @Override
             @UnsupportedAppUsage
             public boolean enabledFixedRo() {
-                return getValue(Flags.FLAG_ENABLED_FIXED_RO);
+                return getValue(Flags.FLAG_ENABLED_FIXED_RO,
+                    FeatureFlags::enabledFixedRo);
             }
             @Override
             @UnsupportedAppUsage
             public boolean enabledRo() {
-                return getValue(Flags.FLAG_ENABLED_RO);
+                return getValue(Flags.FLAG_ENABLED_RO,
+                    FeatureFlags::enabledRo);
             }
             @Override
             @UnsupportedAppUsage
             public boolean enabledRw() {
-                return getValue(Flags.FLAG_ENABLED_RW);
-            }
-            public void setFlag(String flagName, boolean value) {
-                if (!this.mFlagMap.containsKey(flagName)) {
-                    throw new IllegalArgumentException("no such flag " + flagName);
-                }
-                this.mFlagMap.put(flagName, value);
-            }
-            public void resetAll() {
-                for (Map.Entry entry : mFlagMap.entrySet()) {
-                    entry.setValue(null);
-                }
+                return getValue(Flags.FLAG_ENABLED_RW,
+                    FeatureFlags::enabledRw);
             }
+
             public boolean isFlagReadOnlyOptimized(String flagName) {
                 if (mReadOnlyFlagsSet.contains(flagName) &&
                     isOptimizationEnabled()) {
@@ -1082,27 +1151,27 @@ mod tests {
                 }
                 return false;
             }
+
             @com.android.aconfig.annotations.AssumeTrueForR8
             private boolean isOptimizationEnabled() {
                 return false;
             }
-            private boolean getValue(String flagName) {
-                Boolean value = this.mFlagMap.get(flagName);
-                if (value == null) {
-                    throw new IllegalArgumentException(flagName + " is not set");
-                }
-                return value;
-            }
-            private Map<String, Boolean> mFlagMap = new HashMap<>(
-                Map.ofEntries(
-                    Map.entry(Flags.FLAG_DISABLED_RO, false),
-                    Map.entry(Flags.FLAG_DISABLED_RW, false),
-                    Map.entry(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE, false),
-                    Map.entry(Flags.FLAG_ENABLED_FIXED_RO, false),
-                    Map.entry(Flags.FLAG_ENABLED_RO, false),
-                    Map.entry(Flags.FLAG_ENABLED_RW, false)
-                )
-            );
+
+            protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
+                return mGetValueImpl.test(flagName, getter);
+            }
+
+            public List<String> getFlagNames() {
+                return Arrays.asList(
+                    Flags.FLAG_DISABLED_RO,
+                    Flags.FLAG_DISABLED_RW,
+                    Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
+                    Flags.FLAG_ENABLED_FIXED_RO,
+                    Flags.FLAG_ENABLED_RO,
+                    Flags.FLAG_ENABLED_RW
+                );
+            }
+
             private Set<String> mReadOnlyFlagsSet = new HashSet<>(
                 Arrays.asList(
                     Flags.FLAG_DISABLED_RO,
@@ -1116,11 +1185,16 @@ mod tests {
             );
         }
         "#;
+
         let mut file_set = HashMap::from([
             ("com/android/aconfig/test/Flags.java", expect_flags_content),
             ("com/android/aconfig/test/FeatureFlagsImpl.java", expect_featureflagsimpl_content),
             ("com/android/aconfig/test/FeatureFlags.java", expect_featureflags_content),
-            ("com/android/aconfig/test/FakeFeatureFlagsImpl.java", expect_fakefeatureflags_content),
+            ("com/android/aconfig/test/CustomFeatureFlags.java", expect_customfeatureflags_content),
+            (
+                "com/android/aconfig/test/FakeFeatureFlagsImpl.java",
+                EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
+            ),
         ]);
 
         for file in generated_files {
diff --git a/tools/aconfig/aconfig/templates/CustomFeatureFlags.java.template b/tools/aconfig/aconfig/templates/CustomFeatureFlags.java.template
new file mode 100644
index 0000000000..b82b9cb827
--- /dev/null
+++ b/tools/aconfig/aconfig/templates/CustomFeatureFlags.java.template
@@ -0,0 +1,70 @@
+package {package_name};
+
+{{ if not library_exported- }}
+// TODO(b/303773055): Remove the annotation after access issue is resolved.
+import android.compat.annotation.UnsupportedAppUsage;
+{{ -endif }}
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.function.BiPredicate;
+import java.util.function.Predicate;
+
+/** @hide */
+public class CustomFeatureFlags implements FeatureFlags \{
+
+    private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
+
+    public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) \{
+        mGetValueImpl = getValueImpl;
+    }
+
+{{ -for item in flag_elements}}
+    @Override
+{{ if not library_exported }}    @UnsupportedAppUsage{{ -endif }}
+    public boolean {item.method_name}() \{
+        return getValue(Flags.FLAG_{item.flag_name_constant_suffix},
+            FeatureFlags::{item.method_name});
+    }
+{{ endfor }}
+
+{{ -if not library_exported }}
+    public boolean isFlagReadOnlyOptimized(String flagName) \{
+        if (mReadOnlyFlagsSet.contains(flagName) &&
+            isOptimizationEnabled()) \{
+                return true;
+        }
+        return false;
+    }
+
+    @com.android.aconfig.annotations.AssumeTrueForR8
+    private boolean isOptimizationEnabled() \{
+        return false;
+    }
+{{ -endif }}
+
+    protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) \{
+        return mGetValueImpl.test(flagName, getter);
+    }
+
+    public List<String> getFlagNames() \{
+        return Arrays.asList(
+            {{ -for item in flag_elements }}
+            Flags.FLAG_{item.flag_name_constant_suffix}
+            {{ -if not @last }},{{ endif }}
+            {{ -endfor }}
+        );
+    }
+
+    private Set<String> mReadOnlyFlagsSet = new HashSet<>(
+        Arrays.asList(
+            {{ -for item in flag_elements }}
+            {{ -if not item.is_read_write }}
+            Flags.FLAG_{item.flag_name_constant_suffix},
+            {{ -endif }}
+            {{ -endfor }}
+            ""{# The empty string here is to resolve the ending comma #}
+        )
+    );
+}
diff --git a/tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template b/tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template
index 177e711e77..c20d3c5061 100644
--- a/tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template
+++ b/tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template
@@ -1,27 +1,30 @@
 package {package_name};
-{{ if not library_exported- }}
-// TODO(b/303773055): Remove the annotation after access issue is resolved.
-import android.compat.annotation.UnsupportedAppUsage;
-{{ -endif }}
-import java.util.Arrays;
+
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.Map;
-import java.util.Set;
+import java.util.function.Predicate;
 
 /** @hide */
-public class FakeFeatureFlagsImpl implements FeatureFlags \{
+public class FakeFeatureFlagsImpl extends CustomFeatureFlags \{
+    private Map<String, Boolean> mFlagMap = new HashMap<>();
+
     public FakeFeatureFlagsImpl() \{
-        resetAll();
+        super(null);
+        // Initialize the map with null values
+        for (String flagName : getFlagNames()) \{
+            mFlagMap.put(flagName, null);
+        }
     }
 
-{{ for item in flag_elements}}
     @Override
-{{ if not library_exported }}    @UnsupportedAppUsage{{ -endif }}
-    public boolean {item.method_name}() \{
-        return getValue(Flags.FLAG_{item.flag_name_constant_suffix});
+    protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) \{
+        Boolean value = this.mFlagMap.get(flagName);
+        if (value == null) \{
+            throw new IllegalArgumentException(flagName + " is not set");
+        }
+        return value;
     }
-{{ endfor}}
+
     public void setFlag(String flagName, boolean value) \{
         if (!this.mFlagMap.containsKey(flagName)) \{
             throw new IllegalArgumentException("no such flag " + flagName);
@@ -34,46 +37,4 @@ public class FakeFeatureFlagsImpl implements FeatureFlags \{
             entry.setValue(null);
         }
     }
-{{ if not library_exported }}
-    public boolean isFlagReadOnlyOptimized(String flagName) \{
-        if (mReadOnlyFlagsSet.contains(flagName) &&
-            isOptimizationEnabled()) \{
-                return true;
-        }
-        return false;
-    }
-
-    @com.android.aconfig.annotations.AssumeTrueForR8
-    private boolean isOptimizationEnabled() \{
-        return false;
-    }
-{{ -endif }}
-    private boolean getValue(String flagName) \{
-        Boolean value = this.mFlagMap.get(flagName);
-        if (value == null) \{
-            throw new IllegalArgumentException(flagName + " is not set");
-        }
-        return value;
-    }
-
-
-    private Map<String, Boolean> mFlagMap = new HashMap<>(
-        Map.ofEntries(
-            {{ -for item in flag_elements }}
-            Map.entry(Flags.FLAG_{item.flag_name_constant_suffix}, false)
-            {{ -if not @last }},{{ endif }}
-            {{ -endfor }}
-        )
-    );
-
-    private Set<String> mReadOnlyFlagsSet = new HashSet<>(
-        Arrays.asList(
-            {{ -for item in flag_elements }}
-            {{ -if not item.is_read_write }}
-            Flags.FLAG_{item.flag_name_constant_suffix},
-            {{ -endif }}
-            {{ -endfor }}
-            ""{# The empty string here is to resolve the ending comma #}
-        )
-    );
 }