Java自学-String(1)

1、String概述

2、String构造方法

package lesson01;

/**
 * Author: Gu Jiakai
 * Date: 2021/8/12 17:36
 * FileName: StringDemo01
 * Description:
 */
public class StringDemo01 {
    public static void main(String[] args) {
        String s1 = new String();
        System.out.println("s1:"+s1);

        char[] chs={'a','b','c'};
        String s2 = new String(chs);
        System.out.println("s2:"+s2);

        byte[] bys={97,98,99};
        String s3 = new String(bys);
        System.out.println("s3:"+s3);

        String s4="abcd";
        System.out.println("s4:"+s4);
    }
}

3、String对象的特点

4、字符串的比较

5、用户登录

package lesson01;

import java.util.Scanner;

/**
 * Author: Gu Jiakai
 * Date: 2021/8/12 17:54
 * FileName: StringDemo02
 * Description:
 */
public class StringDemo02 {
    public static void main(String[] args) {
        String username="19130104";
        String password="123456";

        Scanner sc = new Scanner(System.in);

        for (int i = 0; i < 3; i++) {
            System.out.println("请输入用户名：");
            String name=sc.nextLine();
            System.out.println("请输入密码：");
            String pwd=sc.nextLine();

            if(name.equals(username)&&pwd.equals(password)){
                System.out.println("登录成功！");
                break;
            }else{
                if(2-i==0){
                    System.out.println("你的账户已被锁定，请联系管理员！");
                }else {
                    System.out.println("登录失败，你还有" + (2 - i) + "次机会！");
                }
            }
        }


    }
}

6、遍历字符串

package lesson01;

import java.util.Scanner;

/**
 * Author: Gu Jiakai
 * Date: 2021/8/12 18:08
 * FileName: StringDemo03
 * Description:
 */
public class StringDemo03 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        System.out.println("请输入一个字符串：");
        String s = sc.nextLine();

        for (int i = 0; i < s.length(); i++) {
            System.out.println(s.charAt(i));
        }
    }
}