逗号,分号;与for循环...

public class CommaOperator { public static void main(String[] args) { for (int i = 1, j = i + 10; i < 5; i++, j = i * 2) { System.out.println("i= " + i + " j= " + j); } } }

 

打印:

 

i= 1 j= 11 i= 2 j= 4 i= 3 j= 6 i= 4 j= 8  

 

理解:

 

int i = 1, j = i + 10; i < 5; i++, j = i * 2

 

第一次打印:

i = 1 ,j = 1+10  -->   ;   -->  i= 1<5(true);     :  i = 1  j = 11

第二次打印:

i++ = 2, j = 2 * 2 --> ;  -->  i=2<5(true);      :  i= 2   j= 4

第三次打印:

i++ = 3, j = 3 * 2 --> ;  -->  i = 3<5(true);    :  i = 3  j = 6

第四次打印:

i++ = 4 j = 4  *2 --> ;  -->  i = 4 <5(true);    :  i = 4 j = 8

第五次打印:

i++ = 5 j = 5 *2 --> ;  -->  i = 5  <5(false);    :  stop

 

 

 public class CommaOperator { public static void main(String[] args) { for (int i = 1, j = i + 10; i < 5; i++, j = i * 2) { System.out.println("i= " + i + " j= " + j); } System.out.println(" ------------------ "); int m = 1; int n = m + 10; while (m < 5) { System.out.println("m= " + m + " n= " + n); m ++ ; n = m *2; } } }

 

 

i= 1 j= 11 i= 2 j= 4 i= 3 j= 6 i= 4 j= 8 ------------------ m= 1 n= 11 m= 2 n= 4 m= 3 n= 6 m= 4 n= 8