Add private empty constructor to static-only classes

It improves the code and method test coverage.

Bug: 157257292
Test: m droid
Test: atest CtsIcuTestCases:com.android
Change-Id: Ib59a0c7db92a4453cf390a775c27f8faa633fff0

4 files changed, 12 insertions, 0 deletions

diff --git a/android_icu4j/libcore_bridge/src/java/com/android/i18n/system/AppSpecializationHooks.java b/android_icu4j/libcore_bridge/src/java/com/android/i18n/system/AppSpecializationHooks.java
index 9be6a0e1b..ea13da4be 100644
--- a/android_icu4j/libcore_bridge/src/java/com/android/i18n/system/AppSpecializationHooks.java
+++ b/android_icu4j/libcore_bridge/src/java/com/android/i18n/system/AppSpecializationHooks.java
@@ -27,6 +27,9 @@ import libcore.api.IntraCoreApi;
 @IntraCoreApi
 public class AppSpecializationHooks {
 
+    /** All methods are static, no need to instantiate. */
+    private AppSpecializationHooks() {}
+
     /**
      * This is a good place to change system properties / clear cache due to an app compat change
      * before an app starts. It's called by
diff --git a/android_icu4j/libcore_bridge/src/java/com/android/i18n/util/Log.java b/android_icu4j/libcore_bridge/src/java/com/android/i18n/util/Log.java
index ae368dcd1..4550a587c 100644
--- a/android_icu4j/libcore_bridge/src/java/com/android/i18n/util/Log.java
+++ b/android_icu4j/libcore_bridge/src/java/com/android/i18n/util/Log.java
@@ -22,6 +22,9 @@ package com.android.i18n.util;
  * @hide
  */
 public class Log {
+    /** All methods are static, no need to instantiate. */
+    private Log() {}
+
     // liblog's log priorities from android_LogPriority in log.h.
     private static int VERBOSE = 2;
     private static int DEBUG = 3;
diff --git a/android_icu4j/libcore_bridge/src/java/com/android/icu/charset/NativeConverter.java b/android_icu4j/libcore_bridge/src/java/com/android/icu/charset/NativeConverter.java
index ffbcb7de6..1159e6827 100644
--- a/android_icu4j/libcore_bridge/src/java/com/android/icu/charset/NativeConverter.java
+++ b/android_icu4j/libcore_bridge/src/java/com/android/icu/charset/NativeConverter.java
@@ -21,6 +21,9 @@ public final class NativeConverter {
     private static final NativeAllocationRegistry registry = NativeAllocationRegistry
         .createMalloced(NativeConverter.class.getClassLoader(), getNativeFinalizer());
 
+    /** All methods are static, no need to instantiate. */
+    private NativeConverter() {}
+
     /* package */ static native int decode(long converterHandle, byte[] input, int inEnd,
             char[] output, int outEnd, int[] data, boolean flush);
 
diff --git a/android_icu4j/libcore_bridge/src/java/com/android/icu/text/CompatibleDecimalFormatFactory.java b/android_icu4j/libcore_bridge/src/java/com/android/icu/text/CompatibleDecimalFormatFactory.java
index 97d81818a..a2f254d27 100644
--- a/android_icu4j/libcore_bridge/src/java/com/android/icu/text/CompatibleDecimalFormatFactory.java
+++ b/android_icu4j/libcore_bridge/src/java/com/android/icu/text/CompatibleDecimalFormatFactory.java
@@ -31,6 +31,9 @@ import libcore.api.IntraCoreApi;
 @IntraCoreApi
 public class CompatibleDecimalFormatFactory {
 
+    /** All methods are static, no need to instantiate. */
+    private CompatibleDecimalFormatFactory() {}
+
     /**
      * Creates an instance compatible with {@link java.text.DecimalFormat}.
      *