Java 实现字符串反转

方法一：

public class StringReverse {  
      
    public void swap(char[] arr, int begin, int end) {  
        while(begin < end) {  
            char temp = arr[begin];  
            arr[begin] = arr[end];  
            arr[end] = temp;  
            begin++;  
            end--;  
        }  
    }  
    //I love java  
    public String swapWords(String str) {  
        char[] arr = str.toCharArray();  
        swap(arr, 0, arr.length - 1);  
        int begin = 0;  
        for (int i = 1; i < arr.length; i++) {  
            if (arr[i] == ' ') {  
                swap(arr, begin, i - 1);  
                begin = i + 1;  
            }  
        }  
  
        return new String(arr);  
    }  
      
    public static void main(String[] args) {  
        String str = "I love java";  
        System.out.println(new StringReverse().swapWords(str));  
    }  
  
}  

方法二：利用JDK提供的方法

public class Main {  
  
    public static void main(String[] args) {  
        Scanner sc = new Scanner(System.in);  
          
        String str = sc.nextLine();  
          
        String[] sArr = str.split(" ");//I love java  
          
        List<String> list = new ArrayList<String>();  
          
        list = Arrays.asList(sArr);  
          
//      for(int i=0;i<sArr.length;i++){  
//          list.add(sArr[i]);  
//      }  
          
        Collections.reverse(list);  
          
        for(String word:list){  
            System.out.print(word+" ");  
        }  
    }  
}  

如果描述改一下，输入一个字符串，例如“abcd”,输出"dcba"

public static String reverse(String str){  
        return new StringBuilder(str).reverse().toString();  
    }

   public void test09() {  
        String str = "hello";  
  
        for (int i = str.length() - 1; i >= 0; i--) {  
              
            char c = str.charAt(i);  
              
            System.out.print(c);  
        }  
    }