Java 实现字符串反转

Posted 2021-02-12 Ainsliaea

1. 使用现成的 reverse() 方法

StringBuilder sb1 = new StringBuilder("Hello you");
System.out.println(sb1.reverse()); //uoy olleH

StringBuffer sb2 = new StringBuffer("haha go");
System.out.println(sb2.reverse()); //og ahah

2. 将字符串转换成字符数组，然后从末尾开始，拼接字符串

void re(String str){
    char[] charStr = str.toCharArray();

    StringBuilder sb = new StringBuilder();
    for (int i = charStr.length - 1; i >= 0; i--) {
        sb.append(charStr[i]);
    }
    System.out.println(sb);
}

3. 对于整数，一种是可以转换成字符串，另外也可以通过取余和除直接倒置

void re(int num){
    int res = 0;
    while(num > 0){
        res = res * 10 + num % 10;
        num /= 10;
    }
    System.out.println(res);
}

 

void re(int num){    int res = 0;    while(num > 0){        // System.out.println("num is " + num);        res = res * 10 + num % 10;        num /= 10;    }    System.out.println(res);}