JAVA控制流程

Java代码有三种执行结构流程，顺序结构、分支结构、循环结构

顺序结构

顺序结构是最简单的代码执行结构，从代码开始逐步执行每一句代码到结束

 public class C {
     public static void main(String[] args){

         String name = "白客C";
         String str = "你好，";

         System.out.printf(str+name);
     }
 }

分支结构

分支结构需要用到条件语句if、switch

if多分支语句

 import java.io.*;

 public class C {
     public static void main(String[] args){

         //实例1
         float f =1.33f;
         if(!(f % 1 == f))
         {
             System.out.println("是小数");
         }

         //实例2
         int a=2, b=3;
         if(a>b)
         {
             System.out.println("a大于b");
         }
         else
         {
             System.out.println("a小于b");
         }

         //实例3
         try{
             InputStreamReader isr = new InputStreamReader(System.in);
             BufferedReader br = new BufferedReader(isr);

             System.out.printf("请输入您的分数：");
             String str = br.readLine();
             int num = Integer.parseInt(str);

             if(num <= 100 && num >= 90)
             {
                 System.out.printf("优秀");
             }else if(num < 90 && num >= 80)
             {
                 System.out.printf("良好");
             }else if(num < 80 && num >= 70)
             {
                 System.out.printf("中");
             }else if(num < 70 && num >= 60)
             {
                 System.out.printf("及格");
             }else
             {
                 System.out.printf("不及格");
             }

         }catch (Exception e){

         }
     }
 }

switch语句

switch语句与if语句的实例3功能一样

 import java.io.*;

 public class C {
     public static void main(String[] args){

         try{
             InputStreamReader isr = new InputStreamReader(System.in);
             BufferedReader br = new BufferedReader(isr);

             System.out.printf("请输入您的分数：");
             String str = br.readLine();
             int num = Integer.parseInt(str);

             switch (num % 10)
             {
                 case 10:
                 case 9:
                     System.out.printf("优秀");
                     break;
                 case 8:
                     System.out.printf("良好");
                     break;
                 case 7:
                     System.out.printf("中");
                     break;
                 case 6:
                     System.out.printf("及格");
                     break;
                 default:
                     System.out.printf("不及格");
             }
         }catch (Exception e){

         }
     }
 }

循环结构

循环结构就重复执行某段语句块，有for循环语句、while循环语句、do-while循环语句

for循环语句

 public class C {
     public static void main(String[] args){
         int num = 0;
         for(int i = 1 ; i <= 100 ; i++)
         {
             num += i;
         }
         String str = String.valueOf(num);
         System.out.print("i=" + str );
     }
 }

while循环语句

 public class C {
     public static void main(String[] args){
         int i = 1;
         int num = 0;
         while ( i <= 100 )
         {
             num += i;
             i++;
         }
         String str = String.valueOf(num);
         System.out.print("i=" + str );
     }
 }

do-while循环语句

do-while会先执行一次

 public class C {
     public static void main(String[] args){
         int i = 1;
         int num = 0;

        do{
            num += i;
            i++;
        }while (i<=100);

         String str = String.valueOf(num);
         System.out.print("i=" + str );
     }
 }