1.break的用法
break语句主要用于switch语句和循环结构。在循环结构中，如果执行了break语句，那么就退出循环，接着执行循环结构下面的第一条语句。如果是嵌套循环，那么break就只跳出它所在的那一层循环，对于外层的任何一个循环都无能为力。
public class BreakDemo {
public static void break1 (){
for(int i = 0; i < 10; i++){
for(int j = 0; j < 10 ;j++){
System.out.println("这是第"+j+"次输出");
break;//这里的break只可以退出内层的for循环
}
}
}
public static void main(String[] args) {
break1();
}
}
其运行结果如上图。分析：在每次进入内层for循环的时候，j的值均为0，而输出完结果之后就直接由break语句把内层for循环跳出，又由于外层for循环要循环十次，所以就有十个输出结果
2continue的用法：
continue语句并没有真正的退出循环，而是只结束了本次循环的执行，开始对下一个循环条件进行判断，
for循环下的continue用法实例代码如下：
package com.xunhuanDemo;
public class Continue {
public static void continue1(){
for(int i = 0; i < 10; i++){
for (int j = 0; j < 10; j++) {
if(j == 7){//如果把这里的if换成while运行结果是有区别的
continue;
}
System.out.println("this is j:"+j);
}
System.out.println("this is i"+i);
}
}
public static void main(String[] args) {
continue1();
}
}
运行结果如下：
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i0
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i1
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i2
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i3
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i4
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i5
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i6
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i7
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i8
this is j:0
this is j:1
this is j:2
this is j:3
this is j:4
this is j:5
this is j:6
this is j:8
this is j:9
this is i9这里发现，每一次输出j是没有等于7的时候，是因为当j == 7时，就因为continue语句的原因直接跳出了内层循环。但是不影响下面当j ==8,9,10时候的输出。因为continue只是使得程序跳出当前本次条件下的一层循环，并不会对接下来的循环造成影响。
while循环下的continue代码实例如下：
package com.xunhuanDemo;
public class Continue {
/*public static void continue1(){
for(int i = 0; i < 10; i++){
for (int j = 0; j < 10; j++) {
if(j == 7){//如果把这里的if换成while运行结果是有区别的
continue;
}
System.out.println("this is j:"+j);
}
System.out.println("this is i"+i);
}
}*/
public static void continue2(){
int i = 0;
while(i < 10){
i++;
if(i == 5){
continue;
}else{
System.out.println(i);
}
}
}
public static void main(String[] args) {
continue2();
}
}
运行结果如下：
由运行结果可以看出，while循环中使用continue和for循环中使用continue的效果是一样的，都是跳出本次本条件下的循环，对之后的循环没有造成影响。
3.return语句
如果在程序中遇到return语句，那么代码就退出该函数的执行，返回到函数的调用处，如果是main()函数，那么结束整个程序的运行。
代码如下：
package com.xunhuanDemo;
public class returnDemo {
public static void return1(){
for (int i = 0; i < 10; i++) {
System.out.println("i的值为:"+i);
if(i == 6){
return;
}
}
System.out.println("第6次的时候已经去了主方法");
}
public static void main(String[] args) {
return1();
System.out.println("第6次之后，这句话输出");
}
}
其运行结果如下：
可见，当i == 6时，由于return语句的作用，使得函数return1（）不再向下运行，而是直接返回到了主方法main（）方法，然后输出了main方法中的那句话。