Java算法基础-逆序算法

package com.seatel.testjava;

import java.util.Stack;

/**
* 关于java算法
*/
public class myClass {

public static void main(String[] args) {
String string = "123abc";

System.out.println(string);

//非静态方法(非static的方法要先new一个对象才能调用)
myClass m = new myClass();
string = m.reverse1(string);

//静态方法(static方法可通过类名.方法名的方式调用)
String string1 = reverse2(string);

System.out.println(string);
System.out.println(string1);
}

//字符串逆序的方法
public String reverse1(String string) {
StringBuffer sb = new StringBuffer();
for (int i = string.length() - 1; i >= 0; i--) {
sb.append(string.charAt(i));
}
return sb.toString();
}

public static String reverse2(String string) {
StringBuffer sb = new StringBuffer(string);
for (int i = 0, j = sb.length() - 1; i < sb.length() >>> 1; i++, j--) {
char temp = sb.charAt(i);
//首
sb.setCharAt(i, sb.charAt(j));
//尾
sb.setCharAt(j, temp);
}
return sb.toString();
}

public static String reverse3(String string) {
StringBuffer sb = new StringBuffer();
Stack<Character> s = new Stack<Character>();
for (int i = 0; i < string.length(); i++) {
s.add(string.charAt(i));
}
for (int i = 0; i < string.length(); i++) {
sb.append(s.pop());
}
return sb.toString();
}
}