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, , arr.length - );
        int begin = ;
        for (int i = ; i < arr.length; i++) {
            if (arr[i] == ' ') {
                swap(arr, begin, i - );
                begin = i + ;
            }
        }  

        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() - ; i >= ; i--) {  

            char c = str.charAt(i);  

            System.out.print(c);
        }
    }