反转字符串

package demo;

import org.junit.Test;

/**
 * 反转字符串
 * Created with IntelliJ IDEA.
 * User: chen_daoliang
 * Date: 2018/9/17
 * Time: 12:37
 * To change this template use File | Settings | File and Code Templates.
 */
public class StringTest {

    public String reverse1(String str) {
        return new StringBuilder(str).reverse().toString();
    }

    public String reverse2(String str) {
        char[] arr = str.toCharArray();
        for (int i = 0, j = arr.length - 1; i < j; i++, j--) {
            char temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
        }
        return new String(arr);
    }

    public String reverse3(String str) {
        StringBuilder sb = new StringBuilder();
        for (int i = str.length() - 1; i >= 0; i--) {
            sb.append(str.charAt(i));
        }
        return sb.toString();
    }

    @Test
    public void test() {
        System.out.println(reverse1("hello"));
        System.out.println(reverse2("hello"));
        System.out.println(reverse3("hello"));
    }
}