Java循环

 1 import java.util.Scanner;
 2 //if循环
 3 public class Demo10 {
 4     public static void main(String[] args) {
 5         //判断考试分数，大于60就是及格，小于60就是不及格
 6         Scanner scanner = new Scanner(System.in);
 7         System.out.println("请输入成绩：");
 8         int score=scanner.nextInt();
 9         if (score<60&&score>=0){
10             System.out.println("不及格");
11         }else if (score>60 &&score<70){
12             System.out.println("及格");
13         }else if (score>70 && score<80){
14             System.out.println("中等");
15         }else if (score>80&&score<90){
16             System.out.println("良好");
17         }else if (score>902&&score<100){
18             System.out.println("优秀");
19         }else if (score==100){
20             System.out.println("满分！");
21         }else{
22             System.out.println("成绩不合法");
23         }
24         scanner.close();
25     }
26 }

 1 public class Demo11 {
 2     public static void main(String[] args) {
 3         //while(){}
 4         int a =0;
 5         while( a < 10 ){
 6             System.out.print(a+"\t");
 7             a++;
 8         }
 9         System.out.println();
10         System.out.println("===========================");
11 
12 
13         //do{}while()
14         int b=0;
15         do {
16             System.out.print(b+"\t");
17             b++;
18         }while(b<10);
19         System.out.println();
20         System.out.println("===========================");
21 
22 
23         //for(){}
24         for (int c=0;c<10;c++){
25             System.out.print(c+"\t");
26         }
27         System.out.println();
28         System.out.println("===========================");
29 
30     }
31 }

 1 //增强for循环：遍历数组
 2         int[] numbers= {10,20,30,40,50};    //定义一个数组
 3         //for循环写法
 4         for(int i=0;i<5;i++){
 5             System.out.print(numbers[i]);
 6             System.out.print(‘\t‘);
 7         }
 8         System.out.println();
 9         System.out.println("===========================");
10         //增强for循环写法   for (int x:numbers)相当于for x in numbers[]
11         for (int x:numbers){
12             System.out.print(x);
13             System.out.print(‘\t‘);
14         }

 1 public class Demo12 {
 2     public static void main(String[] args) {
 3         //根据成绩的等级判断成绩的好坏
 4         char grade = ‘C‘;
 5 
 6         switch (grade){
 7             case ‘A‘:
 8                 System.out.println("优秀");
 9                 break;      //每个case下面都要加上break;  否则会出现case穿透的错误
10             case ‘B‘:
11                 System.out.println("良好");
12                 break;
13             case ‘C‘:
14                 System.out.println("及格");
15                 break;
16             case ‘D‘:
17                 System.out.println("差");
18                 break;
19             default:
20                 System.out.println("未知等级");
21         }
22     }
23 }

 1 public class Demo13 {
 2     public static void main(String[] args) {
 3         int i =0;
 4         while (i<100){
 5             i++;
 6             if (i%10==0){
 7                 System.out.println();
 8                 continue;   //continue在这里就是当i%10为0的时候就跳出当前循环，也就是不执行System.out.print(i);
 9             }
10             System.out.print(i);
11         }
12     }
13 }