src/java.base/share/classes/java/lang/String.java

rev 49004 : 8197594: String#repeat

@@ -2961,10 +2961,56 @@
      *          guaranteed to be from a pool of unique strings.
      * @jls 3.10.5 String Literals
      */
     public native String intern();
 
+    /**
+     * Returns a string whose value is the concatenation of this
+     * string repeated {@code count} times.
+     * <p>
+     * If count or length is zero then the empty string is returned.
+     * <p>
+     * This method may be used to create space padding for
+     * formatting text or zero padding for formatting numbers.
+     * @param   count number of times to repeat
+     * @return  A string composed of this string repeated
+     *          {@code count} times or the empty string if count
+     *          or length is zero.
+     * @throws  IllegalArgumentException if the {@code count} is
+     *          negative.
+     */
+    public String repeat(int count) {
+        if (count < 0) {
+            throw new IllegalArgumentException("count is negative, " + count);
+        }
+        if (count == 1) {
+            return this;
+        }
+        final int len = value.length;
+        if (len == 0 || count == 0) {
+            return "";
+        }
+        if (len == 1) {
+            final byte[] single = new byte[count];
+            Arrays.fill(single, value[0]);
+            return new String(single, coder);
+        }
+        if (Integer.MAX_VALUE / count < len) {
+            throw new OutOfMemoryError();
+        }
+        final int limit = len * count;
+        final byte[] multiple = new byte[limit];
+        System.arraycopy(value, 0, multiple, 0, len);
+        int copied = len;
+        for (int next = copied << 1; next < limit && 0 < next; next = next << 1) {
+            System.arraycopy(multiple, 0, multiple, copied, copied);
+            copied = next;
+        }
+        System.arraycopy(multiple, 0, multiple, copied, limit - copied);
+        return new String(multiple, coder);
+    }
+
     ////////////////////////////////////////////////////////////////
 
     /**
      * Copy character bytes from this string into dst starting at dstBegin.
      * This method doesn't perform any range checking.