From e9d7afbe2bf667167614869c7ea10e91f96ffceb Mon Sep 17 00:00:00 2001
From: Edgar Asatryan <17509127+nstdio@users.noreply.github.com>
Date: Wed, 4 Mar 2020 18:11:23 +0400
Subject: [PATCH] [LANG-1523] Avoid unnecessary allocation in wrapIfMissing.
 (#496)

Now `StringUtils#wrapIfMissing(String, char)` and `StringUtils#wrapIfMissing(String, String)` does not allocate buffer when input is already wrapped.
---
 .../org/apache/commons/lang3/StringUtils.java | 27 +++++++++++++++----
 .../apache/commons/lang3/StringUtilsTest.java |  8 ++++--
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/src/main/java/org/apache/commons/lang3/StringUtils.java b/src/main/java/org/apache/commons/lang3/StringUtils.java
index 2668731eb..5c31d7bcd 100644
--- a/src/main/java/org/apache/commons/lang3/StringUtils.java
+++ b/src/main/java/org/apache/commons/lang3/StringUtils.java
@@ -9448,6 +9448,8 @@ public class StringUtils {
      * Wraps a string with a char if that char is missing from the start or end of the given string.
      * </p>
      *
+     * <p>A new {@code String} will not be created if {@code str} is already wrapped.</p>
+     *
      * <pre>
      * StringUtils.wrapIfMissing(null, *)        = null
      * StringUtils.wrapIfMissing("", *)          = ""
@@ -9472,12 +9474,18 @@ public class StringUtils {
         if (isEmpty(str) || wrapWith == CharUtils.NUL) {
             return str;
         }
+        final boolean wrapStart = str.charAt(0) != wrapWith;
+        final boolean wrapEnd = str.charAt(str.length() - 1) != wrapWith;
+        if (!wrapStart && !wrapEnd) {
+            return str;
+        }
+
         final StringBuilder builder = new StringBuilder(str.length() + 2);
-        if (str.charAt(0) != wrapWith) {
+        if (wrapStart) {
             builder.append(wrapWith);
         }
         builder.append(str);
-        if (str.charAt(str.length() - 1) != wrapWith) {
+        if (wrapEnd) {
             builder.append(wrapWith);
         }
         return builder.toString();
@@ -9488,6 +9496,8 @@ public class StringUtils {
      * Wraps a string with a string if that string is missing from the start or end of the given string.
      * </p>
      *
+     * <p>A new {@code String} will not be created if {@code str} is already wrapped.</p>
+     *
      * <pre>
      * StringUtils.wrapIfMissing(null, *)         = null
      * StringUtils.wrapIfMissing("", *)           = ""
@@ -9508,7 +9518,7 @@ public class StringUtils {
      * @param str
      *            the string to be wrapped, may be {@code null}
      * @param wrapWith
-     *            the char that will wrap {@code str}
+     *            the string that will wrap {@code str}
      * @return the wrapped string, or {@code null} if {@code str==null}
      * @since 3.5
      */
@@ -9516,12 +9526,19 @@ public class StringUtils {
         if (isEmpty(str) || isEmpty(wrapWith)) {
             return str;
         }
+
+        final boolean wrapStart = !str.startsWith(wrapWith);
+        final boolean wrapEnd = !str.endsWith(wrapWith);
+        if (!wrapStart && !wrapEnd) {
+            return str;
+        }
+
         final StringBuilder builder = new StringBuilder(str.length() + wrapWith.length() + wrapWith.length());
-        if (!str.startsWith(wrapWith)) {
+        if (wrapStart) {
             builder.append(wrapWith);
         }
         builder.append(str);
-        if (!str.endsWith(wrapWith)) {
+        if (wrapEnd) {
             builder.append(wrapWith);
         }
         return builder.toString();
diff --git a/src/test/java/org/apache/commons/lang3/StringUtilsTest.java b/src/test/java/org/apache/commons/lang3/StringUtilsTest.java
index e7eb5f075..30263de6b 100644
--- a/src/test/java/org/apache/commons/lang3/StringUtilsTest.java
+++ b/src/test/java/org/apache/commons/lang3/StringUtilsTest.java
@@ -3237,7 +3237,9 @@ public class StringUtilsTest {
         assertEquals("/x/y/z/", StringUtils.wrapIfMissing("x/y/z", '/'));
         assertEquals("/x/y/z/", StringUtils.wrapIfMissing("/x/y/z", '/'));
         assertEquals("/x/y/z/", StringUtils.wrapIfMissing("x/y/z/", '/'));
-        assertEquals("/", StringUtils.wrapIfMissing("/", '/'));
+
+        assertSame("/", StringUtils.wrapIfMissing("/", '/'));
+        assertSame("/x/", StringUtils.wrapIfMissing("/x/", '/'));
     }
 
     @Test
@@ -3259,7 +3261,9 @@ public class StringUtilsTest {
         assertEquals("/x/y/z/", StringUtils.wrapIfMissing("x/y/z/", "/"));
         assertEquals("/", StringUtils.wrapIfMissing("/", "/"));
         assertEquals("ab/ab", StringUtils.wrapIfMissing("/", "ab"));
-        assertEquals("ab/ab", StringUtils.wrapIfMissing("ab/ab", "ab"));
+
+        assertSame("ab/ab", StringUtils.wrapIfMissing("ab/ab", "ab"));
+        assertSame("//x//", StringUtils.wrapIfMissing("//x//", "//"));
     }
 
     @Test