Java 学习笔记

1. String 字符串比较

package String_;

public class MyString {
    public static void main(String[] args) {
        char[] chars = {'a', 'b', 'c'};
        String s1 = new String(chars);
        String s2 = new String(chars);
        // == 是比较字符串地址是否相同
        System.out.println(s1 == s2);

        String s3 = "abc";
        String s4 = "abc";
        System.out.println(s3 == s4);
        // equals 比较字符串内容是否相同
        System.out.println(s1.equals(s2));
        System.out.println(s1.equals(s3));
        System.out.println(s2.equals(s4));
        System.out.println(s3.equals(s4));
    }
}

2. 简单的登录程序

package String_;

import java.util.Scanner;

public class login_test {
    public static void main(String[] args) {
        String username = "juanfage";
        String pwd = "ailaopo";

        for (int i = 0; i < 3; i++) {
            Scanner sc = new Scanner(System.in);
            System.out.println("please input your username");
            String name = sc.nextLine();
            System.out.println("please input your password");
            String pswd = sc.nextLine();

            if (username.equals(name) && pwd.equals(pswd)) {
                System.out.println("Login success");
                break;
            } else {
                System.out.println("Login fail, you have " + (2 - i) + " times");
            }
        }
    }
}

输出如下 :