structure

package struct;

import java.util.Scanner;

public class IfDemo01 {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.println("请输入数据:");
        String s = scan.nextLine();
        if (s.equals("Hello")){
            System.out.println(s);
        }
        System.out.println("End");

        scan.close();
    }
}

package struct;

import java.util.Scanner;

public class IfDemo02 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入成绩:");
        double s = scanner.nextDouble();
        if (s>=60){
            System.out.println("及格");
        }else{
            System.out.println("不及格");
        }
        scanner.close();
    }
}

package 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("恭喜满分！");
        } else if (90<=score&&score<100) {
            System.out.println("A");
        }else if(score<90&&score>=80){
            System.out.println("B");
        }else if(score<80&&score>=70){
            System.out.println("C");
        }else if(score<70&&score>=60){
            System.out.println("D");
        }else if(score<60&&score>=0){
            System.out.println("不及格");
        }else {
            System.out.println("输入不合法");
        }

        scanner.close();
    }
}

package struct;

public class SwitchDemo01 {
    public static void main(String[] args) {
        char grade = 'E';
        switch(grade){
            case 'A':
                System.out.println("优秀");
                break;
            case 'B':
                System.out.println("良好");
                break;
            case 'C':
                System.out.println("再接再厉");
                break;
            case 'D':
                System.out.println("及格");
                break;
            case 'E':
                System.out.println("不及格");
                break;
            default:
                System.out.println("输入不合法");
        }
    }
}

package struct;

public class SwitchDemo02 {
    public static void main(String[] args) {
        String name = "德索萨";
        switch(name){
            case "阿迪斯":
                System.out.println("阿迪斯");
                break;
            case "德索萨":
                System.out.println("德索萨");
                break;
            default:
                System.out.println("输入错误");
        }
    }
}

package struct;

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

package struct;

public class WhileDemo02 {
    public static void main(String[] args) {
        while (true){

        }
    }
}

package struct;

public class WhileDemo03 {
    public static void main(String[] args) {
        int i = 0;
        int sum = 0;
        while (i<=100){
            sum = sum + i;
            i++;
        }
        System.out.println(sum);
    }
}

package struct;

public class DoWhileDemo01 {
    public static void main(String[] args) {
        int i = 0;
        int sum = 0 ;
        do {
            sum = sum + i;
            i++;
        }while(i<=100);
        System.out.println(sum);
    }
}

package struct;

public class DoWhileDemo02 {
    public static void main(String[] args) {
        int a = 0;
        while(a<0){
            System.out.println(a);
            a++;
        }
        System.out.println("================");
        do {
            System.out.println(a);
            a++;
        }while(a<0);

    }
}

package struct;

public class ForDemo01 {
    public static void main(String[] args) {
        int a = 1;
        while(a<=100){
            if (a%3==0){
                System.out.println(a);
            }
            a++;
        }
        System.out.println("=================");
        for(int i = 1;i<=100;i++){
            if (i%3==0){
                System.out.println(i);
            }
        }
        for (int i = 0; i < 100; i++) {

        }
        for (int i = 100; i > 0; i--) {

        }
    }
}

package struct;

public class ForDemo02 {
    public static void main(String[] args) {
        int oddsum = 0;
        int evensum = 0;
        for(int i=1;i<=100;i++){
            if (i%2!=0){
                oddsum +=i;
            }
            if (i%2==0){
                evensum +=i;
            }
        }
        System.out.println(oddsum);
        System.out.println(evensum);
        System.out.println("======================");
        oddsum = 0;
        evensum = 0;
        int a = 1;
        while(a<=100){
            if (a%2!=0){
                oddsum +=a;
            }
            if (a%2==0){
                evensum +=a;
            }
            a++;
        }
        System.out.println(oddsum);
        System.out.println(evensum);
    }
}

package struct;

public class ForDemo03 {
    public static void main(String[] args) {
        for (int i=1;i<=1000;i++){
            if (i%5==0){
                System.out.print(i+"\t");
            }
            if (i%(3*5)==0){
                System.out.println();
                //System.out.print("\n");
            }
        }
    }
}

package struct;

public class ForDemo04 {
    public static void main(String[] args) {
        for (int i=1;i<=9;i++){
            for (int a=1;a<=i;a++){
                System.out.print(a+"*"+i+"="+(a*i)+"\t");
            }
            System.out.println();
        }
    }
}

package struct;

public class ForDemo05 {
    public static void main(String[] args) {
        int[] numbers = {10,20,30,40,50};
        for (int x : numbers){
            System.out.println(x);
        }
        System.out.println("==============");
        for (int i=0;i<5;i++){
            System.out.println(numbers[i]);
        }
    }
}

package struct;

public class BreakDemo {
    public static void main(String[] args) {
        for (int i = 1; i <=100; i++){
            System.out.println(i);
            if (i ==20){
                break;
            }
        }
        System.out.println("123");
    }
}

package struct;

public class ContinueDemo {
    public static void main(String[] args) {
        int i = 0;
        while (i<100){
            i++;
            if (i%10==0){
                System.out.println();
                continue;
            }
            System.out.print(i+"\t");
        }
    }
}

package struct;

public class LabelDemo {
    public static void main(String[] args) {
        outer:for (int i=101;i<=150;i++){
            for (int j=2;j<i/2;j++){
                if (i%j==0){
                    continue outer;
                }
            }
            System.out.print(i+" ");
        }
        System.out.println();
        System.out.println("================================================");
        for (int i=101;i<=150;i++){
            int count = 0;
            for (int j=2;j<i/2;j++){
                if (i%j==0){
                    count = 1;
                }
            }
            if (count==0){
                System.out.print(i+" ");
            }
        }
    }
}

package struct;

public class TestDemo {
    public static void main(String[] args) {
        for (int i=1;i<=9;i+=2){
            int a = (9-i)/2;
            for (int a1 = 1; a1 <= a; a1++) {
                System.out.print(" ");
            }
            for (int j=1;j<=i;j++){
                System.out.print("*");
            }
            System.out.println();
        }
        System.out.println("==========================================");
        for (int i = 1; i <=5; i++) {
            for (int j=5; j>=i; j--) {
                System.out.print(" ");
            }
            for (int j = 1; j <=i; j++) {
                System.out.print("*");
            }
            for (int j = 1; j < i; j++) {
                System.out.print("*");
            }
            System.out.println();
        }
    }
}