Revert "Standardize on Array copyOf" (#9400)

This reverts commit 935d099 from PR #9162.

While the original commit was a nice simplification, I learned from
another Googler that there is unfortunately a performance cost to this
(or at least there was last time this change was attempted). Even if it
turns out to be fast on modern Java runtimes, we still care about the
performance on old Android devices.

java/core/src/main/java/com/google/protobuf/BooleanArrayList.java

@@ -197,7 +197,10 @@ public void addBoolean(boolean element) {
     if (size == array.length) {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      boolean[] newArray = new boolean[length];
+
+      System.arraycopy(array, 0, newArray, 0, size);
+      array = newArray;
     }
 
     array[size++] = element;
@@ -216,10 +219,14 @@ private void addBoolean(int index, boolean element) {
     } else {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      boolean[] newArray = new boolean[length];
+
+      // Copy the first part directly
+      System.arraycopy(array, 0, newArray, 0, index);
 
       // Copy the rest shifted over by one to make room
-      System.arraycopy(array, index, array, index + 1, size - index);
+      System.arraycopy(array, index, newArray, index + 1, size - index);
+      array = newArray;
     }
 
     array[index] = element;

java/core/src/main/java/com/google/protobuf/DoubleArrayList.java

@@ -197,7 +197,10 @@ public void addDouble(double element) {
     if (size == array.length) {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      double[] newArray = new double[length];
+
+      System.arraycopy(array, 0, newArray, 0, size);
+      array = newArray;
     }
 
     array[size++] = element;
@@ -216,10 +219,14 @@ private void addDouble(int index, double element) {
     } else {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      double[] newArray = new double[length];
+
+      // Copy the first part directly
+      System.arraycopy(array, 0, newArray, 0, index);
 
       // Copy the rest shifted over by one to make room
-      System.arraycopy(array, index, array, index + 1, size - index);
+      System.arraycopy(array, index, newArray, index + 1, size - index);
+      array = newArray;
     }
 
     array[index] = element;

java/core/src/main/java/com/google/protobuf/FloatArrayList.java

@@ -196,7 +196,10 @@ public void addFloat(float element) {
     if (size == array.length) {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      float[] newArray = new float[length];
+
+      System.arraycopy(array, 0, newArray, 0, size);
+      array = newArray;
     }
 
     array[size++] = element;
@@ -215,10 +218,14 @@ private void addFloat(int index, float element) {
     } else {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      float[] newArray = new float[length];
+
+      // Copy the first part directly
+      System.arraycopy(array, 0, newArray, 0, index);
 
       // Copy the rest shifted over by one to make room
-      System.arraycopy(array, index, array, index + 1, size - index);
+      System.arraycopy(array, index, newArray, index + 1, size - index);
+      array = newArray;
     }
 
     array[index] = element;

java/core/src/main/java/com/google/protobuf/IntArrayList.java

@@ -196,7 +196,10 @@ public void addInt(int element) {
     if (size == array.length) {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      int[] newArray = new int[length];
+
+      System.arraycopy(array, 0, newArray, 0, size);
+      array = newArray;
     }
 
     array[size++] = element;
@@ -215,10 +218,14 @@ private void addInt(int index, int element) {
     } else {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      int[] newArray = new int[length];
+
+      // Copy the first part directly
+      System.arraycopy(array, 0, newArray, 0, index);
 
       // Copy the rest shifted over by one to make room
-      System.arraycopy(array, index, array, index + 1, size - index);
+      System.arraycopy(array, index, newArray, index + 1, size - index);
+      array = newArray;
     }
 
     array[index] = element;

java/core/src/main/java/com/google/protobuf/LongArrayList.java

@@ -196,7 +196,10 @@ public void addLong(long element) {
     if (size == array.length) {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      long[] newArray = new long[length];
+
+      System.arraycopy(array, 0, newArray, 0, size);
+      array = newArray;
     }
 
     array[size++] = element;
@@ -215,10 +218,14 @@ private void addLong(int index, long element) {
     } else {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      long[] newArray = new long[length];
+
+      // Copy the first part directly
+      System.arraycopy(array, 0, newArray, 0, index);
 
       // Copy the rest shifted over by one to make room
-      System.arraycopy(array, index, array, index + 1, size - index);
+      System.arraycopy(array, index, newArray, index + 1, size - index);
+      array = newArray;
     }
 
     array[index] = element;

java/core/src/main/java/com/google/protobuf/ProtobufArrayList.java

@@ -80,7 +80,9 @@ public boolean add(E element) {
     if (size == array.length) {
       // Resize to 1.5x the size
       int length = ((size * 3) / 2) + 1;
-      array = Arrays.copyOf(array, length);
+      E[] newArray = Arrays.copyOf(array, length);
+
+      array = newArray;
     }
 
     array[size++] = element;