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Java - how to reverse a string
2 points
In this post we will take a look how to reverse a string in java. Of course there is more than one way to do it.
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String example = "ABCD"; // we have this string2
String reversed = "DCBA"; // expected - reversed stringCode example:
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String example = "ABCD";2
String reversed = new StringBuilder(example).reverse().toString();3
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System.out.println(example); // ABCD5
System.out.println(reversed); // DCBAOutput:
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ABCD2
DCBACode example:
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public class JavaReverseStringExample2 {2
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public static void main(String[] args) {4
String example = "ABCD";5
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char[] arr = example.toCharArray();7
int j = arr.length - 1;8
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for (int i = 0; i < arr.length / 2; i++, j--) {10
char tmp = arr[i];11
arr[i] = arr[j];12
arr[j] = tmp;13
}14
String reversed = new String(arr);15
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System.out.println(example); // ABCD17
System.out.println(reversed); // DCBA18
}19
}Output:
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ABCD2
DCBACode example:
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public class JavaReverseStringRecursive {2
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public static void main(String[] args) {4
String example = "ABCD";5
String reversed = reverseStringRecursive(example);6
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System.out.println(example); // ABCD8
System.out.println(reversed); // DCBA9
}10
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public static String reverseStringRecursive(String str) {12
if ((null == str) || (str.length() <= 1)) {13
return str;14
}15
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return reverseStringRecursive(str.substring(1)) + str.charAt(0);17
}18
}Output:
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ABCD2
DCBACode example:
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import org.apache.commons.lang3.StringUtils;2
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public class JavaReverseStringApacheCommons {4
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public static void main(String[] args) {6
String example = "ABCD";7
String reversed = StringUtils.reverse(example);8
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System.out.println(example); // ABCD10
System.out.println(reversed); // DCBA11
}12
}Output:
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ABCD2
DCBANOTE:
How Apache commons StringUtils.reverse looks internally:
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public class StringUtils {2
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// ..4
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public static String reverse(final String str) {6
if (str == null) {7
return null;8
}9
return new StringBuilder(str).reverse().toString();10
}11
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// ..13
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}