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Returning a word of a string

I want to flip words to String. I tried to implement it like this:

public String reverseWords(String str) {
    String reverse = "";
    String[] arr = str.split(" ");
    for (int i = arr.length; i < 0; i++) {
        reverse+=arr[i];
    }       
    return reverse;
}

However, does this return nothing to me? Any guidance on what I am doing wrong?

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6 answers


You need to repeat the loop back. using --

and you don't have to go from 0 to length

, but from length

to 1

. This is the basic logic behind the manual reverse function.

try this:



public static String reverseWords(String str) {
    StringBuilder sb = new StringBuilder(str.length() + 1);
    String[] words = str.split(" ");
    for (int i = words.length - 1; i >= 0; i--) {
        sb.append(words[i]).append(' ');
    }
    sb.setLength(sb.length() - 1);  // Strip trailing space
    return sb.toString();
}
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try i=0

before arr.length

or i--

and i>=0

.

Or in more detail:



Do you want to

for (int i=arr.length-1 ; i>=0 ;i--)
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You have: for (int i = arr.length; i < 0; i++) {

I will always be greater than or equal to 0 if it is length.
Try it: for (int i = arr.length; i > 0; i--) {

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if you want to use a loop.

version 1:

public String reverseWords(String str) {
    String reverse = "";
    for (int i = str.length()-1; i >= 0; i--) {
        reverse+=str.charAt(i);
    }       
    return reverse;
}

version 2:

 public String reverseWords(String str) {
StringBuilder sb = new StringBuilder(str.length()+1);
        for (int i = str.length()-1; i >= 0; i--) {
            sb.append(str.charAt(i));
        }       
        return sb.toString();
    }
+2


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if the string is huge, moreover, if you are in a multi-threaded environment, it is recommended to use StringBuffer instead of StringBuilder.

public  String reverseWords(String str) {
          return new StringBuffer(str).reverse().toString();
       }
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I am giving another option for changing the string using charArray in java. 1. copy the whole string to char array using function 2. Just print the character in reverse order.

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