Reverse a string in Java

I have "Hello World" kept in a String variable named hi .

I need to print it, but reversed.

How can I do this? I understand there is some kind of a function already built-in into Java that does that.

Related: Reverse each individual word of “Hello World” string with Java

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You can use this:

new StringBuilder(hi).reverse().toString()

Or, for versions earlier than JDK 1.5, use java.util.StringBuffer instead of StringBuilder — they have the same API. Thanks commentators for pointing out that StringBuilder is preferred nowadays.

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对于不允许使用StringBuilder或StringBuffer Online Judge问题 ，您可以使用char[] 代替它，如下所示：

public static String reverse(String input){
    char[] in = input.toCharArray();
    int begin=0;
    int end=in.length-1;
    char temp;
    while(end>begin){
        temp = in[begin];
        in[begin]=in[end];
        in[end] = temp;
        end--;
        begin++;
    }
    return new String(in);
}

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public static String reverseIt(String source) {
    int i, len = source.length();
    StringBuilder dest = new StringBuilder(len);

    for (i = (len - 1); i >= 0; i--){
        dest.append(source.charAt(i));
    }

    return dest.toString();
}

http://www.java2s.com/Code/Java/Language-Basics/ReverseStringTest.htm

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