Java程序反转句子中的单个单词

Question

I am trying to write a java program that reverses every individual word in a sentence. For example, if the sentence is "Hello World. Hello Java." , the output should be "olleH dlroW. olleH avaJ" . I am able to do the reverse but the output I am getting is "olleH .dlroW olleH .avaJ" where even the dot is getting reversed which should not happen. Can somebody help me fix it?

Thank you!!

I tried something like this:

import java.util.Scanner;

public class ReverseWords {
    public static void main(String[] args) {

        System.out.println("Enter a string to be reversed:");
        Scanner input = new Scanner(System.in);

        String reverse = "";

        while(input.hasNextLine())
        {
            String str = input.next();
            for(int i = str.length()-1; i >= 0; i--)
            {
                reverse = reverse + str.charAt(i);
            }
            reverse += " ";
            System.out.println(reverse);
        }
    }

}

Expected output: olleH dlroW. olleH avaJ.

Output I am getting:

olleH

olleH .dlroW

olleH .dlroW olleH

olleH .dlroW olleH .avaJ

Answer 1

Here is the java 8 solution, you may need to modify replaceChar method if you want to restrict other special characters.

public static void main(String[] args) {
    String str = "Hello World. Hello Java.";
    String collect = Arrays.stream(str.split("\\s+"))  // split sentences into words
            .map(s -> new StringBuffer(s))             // converting to StringBuffer
            .map(s -> s.reverse())                     // reversing the string
            .map(s -> replaceChar(s))                  // replace first char if it is dot
            .collect(Collectors.joining(" "));         // join all the words

    System.out.println(collect);

}

private static String replaceChar(StringBuffer stringBuffer) {
    if(stringBuffer.charAt(0) == '.') {
        stringBuffer.deleteCharAt(0);
        return stringBuffer.toString() + ".";
    }

    return stringBuffer.toString();
}

If you want to do it in the imperative style you can modify your code as below:

String str = "Hello World. Hello Java.";
String[] tokens = str.split("\\s+");
String reverseString = "";
for (String token : tokens) {
    String reverse = "";
    for (int i = token.length() - 1; i >= 0; i--) {
        reverse = reverse + token.charAt(i);
    }
    if(reverse.charAt(0) == '.') {
        reverse = reverse.substring(1) + ".";
    }
    reverseString = reverseString + " " + reverse;
}
System.out.println(reverseString);

Answer 2

Changed a little in your code to handle . in words.

import java.util.Scanner;
public class HelloWorld{
    public static void main(String []args){
        System.out.println("Enter a string to be reversed:");
        Scanner input = new Scanner(System.in);

        String reverse = "";

        while(input.hasNextLine())
        {
            String str = input.next();
            if(str.contains(".")){
                str = str.replace(".","");
                for(int i = str.length()-1; i >= 0; i--)
                {
                    reverse = reverse + str.charAt(i);
                }
                reverse = reverse+".";
            }
            else{
                for(int i = str.length()-1; i >= 0; i--)
                {
                    reverse = reverse + str.charAt(i);
                }
            }
            reverse += " ";
            System.out.println(reverse);
        }
    }
}