Apache
/
commons-lang
mirror of https://github.com/apache/commons-lang.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

LANG-1119: Add StringUtils.rotate(String, int)

This commit is contained in:
Loic Guibert 2015-04-26 16:57:21 +04:00 committed by Benedikt Ritter
parent 0799f01df1
commit 02a98515a3
2 changed files with 62 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

46
src/main/java/org/apache/commons/lang3/StringUtils.java
View File

@ -74,6 +74,8 @@ import java.util.regex.Pattern;
* - checks the characters in a String</li>
* <li><b>DefaultString</b>
* - protects against a null input String</li>
* <li><b>Rotate</b>
* - rotate (circular shift) a String</li>
* <li><b>Reverse/ReverseDelimited</b>
* - reverses a String</li>
* <li><b>Abbreviate</b>
@ -6338,6 +6340,50 @@ public class StringUtils {
return isEmpty(str) ? defaultStr : str;
}
// Rotating (circular shift)
//-----------------------------------------------------------------------
/**
* <p>Rotate (circular shift) a String of {@code shift} characters.</p>
* <ul>
* <li>If {@code shift > 0}, right circular shift (ex : ABCDEF =&gt; FABCDE)</li>
* <li>If {@code shift < 0}, left circular shift (ex : ABCDEF =&gt; BCDEFA)</li>
* </ul>
*
* <pre>
* StringUtils.rotate(null, *) = null
* StringUtils.rotate("", *) = ""
* StringUtils.rotate("abcdefg", 0) = "abcdefg"
* StringUtils.rotate("abcdefg", 2) = "fgabcde"
* StringUtils.rotate("abcdefg", -2) = "cdefgab"
* StringUtils.rotate("abcdefg", 7) = "abcdefg"
* StringUtils.rotate("abcdefg", -7) = "abcdefg"
* StringUtils.rotate("abcdefg", 9) = "fgabcde"
* StringUtils.rotate("abcdefg", -9) = "cdefgab"
* </pre>
*
* @param str the String to rotate, may be null
* @param shift number of time to shift (positive : right shift, negative : left shift)
* @return the rotated String,
* or the original String if {@code shift == 0},
* or {@code null} if null String input
*/
public static String rotate(String str, int shift) {
if (str == null) {
return null;
}
final int strLen = str.length();
if (shift == 0 || strLen == 0 || shift % strLen == 0) {
return str;
}
final StringBuilder builder = new StringBuilder(strLen);
final int offset = - (shift % strLen);
builder.append(substring(str, offset));
builder.append(substring(str, 0, offset));
return builder.toString();
}
// Reversing
//-----------------------------------------------------------------------
/**

16
src/test/java/org/apache/commons/lang3/StringUtilsTest.java
View File

@ -1625,6 +1625,22 @@ public class StringUtilsTest {
assertEquals(" abc ", StringUtils.center("abc", 7, ""));
}
//-----------------------------------------------------------------------
@Test
public void testRotate_StringInt() {
assertEquals(null, StringUtils.rotate(null, 1));
assertEquals("", StringUtils.rotate("", 1));
assertEquals("abcdefg", StringUtils.rotate("abcdefg", 0));
assertEquals("fgabcde", StringUtils.rotate("abcdefg", 2));
assertEquals("cdefgab", StringUtils.rotate("abcdefg", -2));
assertEquals("abcdefg", StringUtils.rotate("abcdefg", 7));
assertEquals("abcdefg", StringUtils.rotate("abcdefg", -7));
assertEquals("fgabcde", StringUtils.rotate("abcdefg", 9));
assertEquals("cdefgab", StringUtils.rotate("abcdefg", -9));
assertEquals("efgabcd", StringUtils.rotate("abcdefg", 17));
assertEquals("defgabc", StringUtils.rotate("abcdefg", -17));
}
//-----------------------------------------------------------------------
@Test
public void testReverse_String() {