java中switch结构和 while for循环的用法

6.2 switch结构：   

变量可以是：variable can be:(mark: tried, can not be long)
char/int/short/byte（java1.7 就可以用String来switch了）

　

public class Test{
  public static void main(String[] args){
    double d1=0.0, d2=0.0;
    d1 = 11;
    d2 = 22;
    char o = '+';
    switch(o){
       case '+':
           System.out.println(d1+d2);
           break;
       case '-':
           System.out.println(d1-d2);
           break;
       case '*':
           System.out.println(d1*d2);
           break;
       case '/':
           System.out.println(d1/d2);
    }
  }
}

result is:

33.0

　

6.3 循环

6.3.1 while 循环

public class Test{
  public static void main(String[] args){
    int lim = 5;
    int sum = 0;
    int i = 1;
    while(i<=lim){
        sum =sum + i;
        i++;
    }
    System.out.println("sum = " + sum);

    int j = 1;
    while(j<=4){
        System.out.println("j=" + j);
        j++;
    }
    System.out.println(j);
  }
}

　

result:

sum = 15
j=1
j=2
j=3
j=4
5

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