break和continue标签的用法

Java中for循环中执行顺序问题及break, continue标签用法

博客分类：

Java综合

Java代码







public class labeledfor {

static test monitor = new test();

public static void main(string[] args) {

int i = 0;

outer: // can't have statements here

for(; true ;) { // infinite loop

inner: // can't have statements here

for(; i < 10; i++) {

system.out.println("i = " + i);

if(i == 2) {

system.out.println("continue");

continue;

}

if(i == 3) {

system.out.println("break");

i++; // otherwise i never

// gets incremented.

break;

}

if(i == 7) {

system.out.println("continue outer");

i++; // otherwise i never

// gets incremented.

continue outer;

}

if(i == 8) {

system.out.println("break outer");

break outer;

}

for(int k = 0; k < 5; k++) {

if(k == 3) {

system.out.println("continue inner");

continue inner;

}

public class labeledfor {
static test monitor = new test();
public static void main(string[] args) {
int i = 0;
outer: // can't have statements here
for(; true ;) { // infinite loop
inner: // can't have statements here
for(; i < 10; i++) {
system.out.println("i = " + i);
if(i == 2) {
system.out.println("continue");
continue;
}
if(i == 3) {
system.out.println("break");
i++; // otherwise i never
// gets incremented.
break;
}
if(i == 7) {
system.out.println("continue outer");
i++; // otherwise i never
// gets incremented.
continue outer;
}
if(i == 8) {
system.out.println("break outer");
break outer;
}

for(int k = 0; k < 5; k++) {
if(k == 3) {
system.out.println("continue inner");
continue inner;
}

结果:
"i = 0",
"continue inner",
"i = 1",
"continue inner",
"i = 2",
"continue",
"i = 3",
"break",
"i = 4",
"continue inner",
"i = 5",
"continue inner",
"i = 6",
"continue inner",
"i = 7",
"continue outer",
"i = 8",
"break outer"

总结：

(1):一般的continue会退回最内层循环的开头（顶部），并继续执行。
(2):带标签的continue会到达标签的位置，并重新进入紧接在那个标签后面的循环。
(3):一般的break会中断并跳出当前的循环。
(4):带标签的break会中断并跳出标签所指的循环。
要记住的重点是：在Java里面需要使用标签的唯一理由是因为有循环嵌套的存在，而且想从多层嵌套中break或continue。