[LANG-1458] Add EMPTY_ARRAY constants to classes in

org.apache.commons.lang3.tuple

4 files changed, 88 insertions, 0 deletions

diff --git a/src/main/java/org/apache/commons/lang3/tuple/ImmutablePair.java b/src/main/java/org/apache/commons/lang3/tuple/ImmutablePair.java
index abc8c3be5..c0934bf1d 100644
--- a/src/main/java/org/apache/commons/lang3/tuple/ImmutablePair.java
+++ b/src/main/java/org/apache/commons/lang3/tuple/ImmutablePair.java
@@ -34,6 +34,28 @@ package org.apache.commons.lang3.tuple;
 public final class ImmutablePair<L, R> extends Pair<L, R> {
 
     /**
+     * An empty array.
+     * <p>
+     * Consider using {@link #emptyArray()} to avoid generics warnings.
+     * </p>
+     *
+     * @since 3.10.
+     */
+    public static final ImmutablePair<?, ?>[] EMPTY_ARRAY = new ImmutablePair[0];
+
+    /**
+     * Returns the empty array singleton that can be assigned without compiler warning.
+     * 
+     * @return the empty array singleton that can be assigned without compiler warning.
+     *
+     * @since 3.10.
+     */
+    @SuppressWarnings("unchecked")
+    public static final <L, R> ImmutablePair<L, R>[] emptyArray() {
+        return (ImmutablePair<L, R>[]) EMPTY_ARRAY;
+    }
+
+    /**
      * An immutable pair of nulls.
      */
     // This is not defined with generics to avoid warnings in call sites.
diff --git a/src/main/java/org/apache/commons/lang3/tuple/ImmutableTriple.java b/src/main/java/org/apache/commons/lang3/tuple/ImmutableTriple.java
index 2d9dda61f..baf4ad174 100644
--- a/src/main/java/org/apache/commons/lang3/tuple/ImmutableTriple.java
+++ b/src/main/java/org/apache/commons/lang3/tuple/ImmutableTriple.java
@@ -35,6 +35,28 @@ package org.apache.commons.lang3.tuple;
 public final class ImmutableTriple<L, M, R> extends Triple<L, M, R> {
 
     /**
+     * An empty array.
+     * <p>
+     * Consider using {@link #emptyArray()} to avoid generics warnings.
+     * </p>
+     *
+     * @since 3.10.
+     */
+    public static final ImmutableTriple<?, ?, ?>[] EMPTY_ARRAY = new ImmutableTriple[0];
+
+    /**
+     * Returns the empty array singleton that can be assigned without compiler warning.
+     * 
+     * @return the empty array singleton that can be assigned without compiler warning.
+     *
+     * @since 3.10.
+     */
+    @SuppressWarnings("unchecked")
+    public static final <L, M, R> ImmutableTriple<L, M, R>[] emptyArray() {
+        return (ImmutableTriple<L, M, R>[]) EMPTY_ARRAY;
+    }
+
+    /**
      * An immutable triple of nulls.
      */
     // This is not defined with generics to avoid warnings in call sites.
diff --git a/src/main/java/org/apache/commons/lang3/tuple/MutablePair.java b/src/main/java/org/apache/commons/lang3/tuple/MutablePair.java
index 386988bf0..1779b5827 100644
--- a/src/main/java/org/apache/commons/lang3/tuple/MutablePair.java
+++ b/src/main/java/org/apache/commons/lang3/tuple/MutablePair.java
@@ -28,6 +28,28 @@ package org.apache.commons.lang3.tuple;
  */
 public class MutablePair<L, R> extends Pair<L, R> {
 
+    /**
+     * An empty array.
+     * <p>
+     * Consider using {@link #emptyArray()} to avoid generics warnings.
+     * </p>
+     *
+     * @since 3.10.
+     */
+    public static final MutablePair<?, ?>[] EMPTY_ARRAY = new MutablePair[0];
+
+    /**
+     * Returns the empty array singleton that can be assigned without compiler warning.
+     * 
+     * @return the empty array singleton that can be assigned without compiler warning.
+     *
+     * @since 3.10.
+     */
+    @SuppressWarnings("unchecked")
+    public static final <L, R> MutablePair<L, R>[] emptyArray() {
+        return (MutablePair<L, R>[]) EMPTY_ARRAY;
+    }
+
     /** Serialization version */
     private static final long serialVersionUID = 4954918890077093841L;
 
diff --git a/src/main/java/org/apache/commons/lang3/tuple/MutableTriple.java b/src/main/java/org/apache/commons/lang3/tuple/MutableTriple.java
index f5d92be76..cfd8bf38c 100644
--- a/src/main/java/org/apache/commons/lang3/tuple/MutableTriple.java
+++ b/src/main/java/org/apache/commons/lang3/tuple/MutableTriple.java
@@ -29,6 +29,28 @@ package org.apache.commons.lang3.tuple;
  */
 public class MutableTriple<L, M, R> extends Triple<L, M, R> {
 
+    /**
+     * The empty array singleton.
+     * <p>
+     * Consider using {@link #emptyArray()} to avoid generics warnings.
+     * </p>
+     *
+     * @since 3.10.
+     */
+    public static final MutableTriple<?, ?, ?>[] EMPTY_ARRAY = new MutableTriple[0];
+    
+    /**
+     * Returns the empty array singleton that can be assigned without compiler warning.
+     * 
+     * @return the empty array singleton that can be assigned without compiler warning.
+     *
+     * @since 3.10.
+     */
+    @SuppressWarnings("unchecked")
+    public static final <L, M, R> MutableTriple<L, M, R>[] emptyArray() {
+        return (MutableTriple<L, M, R>[]) EMPTY_ARRAY;
+    }
+
     /** Serialization version */
     private static final long serialVersionUID = 1L;