顺序结构

选择结构

package com.zhu.struct;

import java.util.Scanner;

public class IfDemo01 {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入内容：");
        String s = scanner.nextLine();
        //equals:判断字符串是否想等
        if (s.equals("Hello")){
            System.out.println(s);
        }
            System.out.println("end");
        scanner.close();
    }
}

package com.zhu.struct;

import java.util.Scanner;

public class IfDemo02 {
    public static void main(String[] args) {
        //考试分数大于60就是及格，小于60分就不及格。
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入考试分数");
        int score = scanner.nextInt();
        if (score<60){
            System.out.println("不及格");
        }
        else{
            System.out.println("及格");
        }
        scanner.close();

    }
}

package com.zhu.struct;

import java.util.Scanner;

public class IfDemo03 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入成绩：");
        int score = scanner.nextInt();
        if (score==100){
            System.out.println("恭喜你获得满分");
        }
        else if(score<100 && score>=90){
            System.out.println("您的等级为A等级");
        }
        else if(score<90 && score>=80){
            System.out.println("您的等级为B等级");
        }
        else if(score<80 && score>=70){
            System.out.println("您的等级为C等级");
        }
        else if(score<70 && score>=60){
            System.out.println("您的等级为D等级");
        }
        else if(score<60 && score>=0){
            System.out.println("您的等级不合格");
        }
        else {
            System.out.println("您输入的分数不合法");
        }

        scanner.close();



    }
}

package com.zhu.struct;

import java.util.Scanner;

public class SwitchDemo01 {
    public static void main(String[] args) {
        //case 穿透  //switch 匹配一个具体的值
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入您的等级");
        char grade = scanner.next().charAt(0);
        switch (grade) {
            case 'A':
                System.out.println("优秀");
                break;
            case 'B':
                System.out.println("良好");
                break;
            case 'C':
                System.out.println("及格");
                break;
            case 'D':
                System.out.println("再接再厉");
                break;
            case 'E':
                System.out.println("挂科");
                break;
            default:
                System.out.println("未知等级");

        }
        scanner.close();
    }
}

package com.zhu.struct;

public class WhileDemo01 {
    public static void main(String[] args) {
        //输出1~100
        int i = 0 ;
        while (i<100){
            i++;
            System.out.println(i);
        }
    }
}

package com.zhu.struct;


public class WhileDemo02 {
    public static void main(String[] args) {
        //死循环
        while(true){
            //等待客户端连接
            //定时检查
            //...........
        }
    }
}

package com.zhu.struct;

public class WhileDemo03 {
    public static void main(String[] args) {
        //计算1加到100；
        int i = 0;
        int sum = 0;
        while (i<=100){
            sum = sum+i;
            i++;

        }
        System.out.println(sum);

    }
}

package com.zhu.struct;

public class DowhileDemo01 {
    public static void main(String[] args) {
        //计算1加到100；
        int i = 0;
        do{
            i++;
        }
        while (i<0);
        System.out.println(i);
    }
}

package com.zhu.struct;


public class ForDemo01 {
    public static void main(String[] args) {
        for (int i = 0; i < 100; i++) {
            System.out.println(i);

        }

    }
}

package com.zhu.struct;


public class ForDemo02 {
    public static void main(String[] args) {
        //计算1-100奇数与偶数的和
        int oddSum = 0;
        int evenSum = 0;
        for (int i = 0; i <= 100; i++) {
            if(i%2!=0){
                oddSum+=i;

            }
            else {
                evenSum+=i;
            }
        }
        System.out.println("奇数和为："+oddSum);
        System.out.println("偶数和为："+evenSum);
    }
}

package com.zhu.struct;


public class ForDemo03 {
    public static void main(String[] args) {
        //用for循环输出1-1000之间能被5整除的数，并且每行输出3个
        for (int i = 1; i <=1000; i++) {
            if(i%5==0){
                System.out.print(i+"\t");
            }
            if(i%15==0){
                System.out.println("\n");
            }
        }
        //println 输出完会换行
        //print 输出完不会换行   \t：等于tab键   \n：换行

    }
}

package com.zhu.struct;


import java.util.Scanner;

public class ForDemo04 {
    public static void main(String[] args) {
        int i = 1;
        //用While循环输出1-1000之间能被5整除的数，并且每行输出3个
        while (i<=1000){
            if(i%5==0){ //判断i能不能被5整除
                System.out.print(i+"\t");//如果能被5整除。则输出i并且空几格

            }
            i++;//i自增，以便进行下一个数的判断
            if(i%15==0){  //判断如果输出的3个数，就换行
                System.out.println("");
            }


        }

    }
}