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[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.
This commit is contained in:
Edgar Asatryan 2020-03-04 18:11:23 +04:00 committed by GitHub
parent 94b3784fde
commit e9d7afbe2b
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 28 additions and 7 deletions
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27
src/main/java/org/apache/commons/lang3/StringUtils.java
View File

@ -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();

8
src/test/java/org/apache/commons/lang3/StringUtilsTest.java
View File

@ -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