它们被保留以供将来使用(请参阅:Java语言关键字)

关键字const和goto是保留的，即使它们目前没有被使用。

Java中没有goto语句的原因可以在“Java语言环境”中找到:

Java has no goto statement. Studies illustrated that goto is (mis)used more often than not simply "because it's there". Eliminating goto led to a simplification of the language--there are no rules about the effects of a goto into the middle of a for statement, for example. Studies on approximately 100,000 lines of C code determined that roughly 90 percent of the goto statements were used purely to obtain the effect of breaking out of nested loops. As mentioned above, multi-level break and continue remove most of the need for goto statements.

它们被保留以供将来使用(请参阅:Java语言关键字)

关键字const和goto是保留的，即使它们目前没有被使用。

Java中没有goto语句的原因可以在“Java语言环境”中找到:

Java has no goto statement. Studies illustrated that goto is (mis)used more often than not simply "because it's there". Eliminating goto led to a simplification of the language--there are no rules about the effects of a goto into the middle of a for statement, for example. Studies on approximately 100,000 lines of C code determined that roughly 90 percent of the goto statements were used purely to obtain the effect of breaking out of nested loops. As mentioned above, multi-level break and continue remove most of the need for goto statements.

关键字存在，但没有实现。

我能想到的使用goto的唯一好理由是:

for (int i = 0; i < MAX_I; i++) {
    for (int j = 0; j < MAX_J; j++) {
        // do stuff
        goto outsideloops; // to break out of both loops
    }
}
outsideloops:

在Java中，你可以这样做:

loops:
for (int i = 0; i < MAX_I; i++) {
    for (int j = 0; j < MAX_J; j++) {
        // do stuff
        break loops;
    }
}

如何在Java中使用"continue"标签的例子是:

public class Label {
    public static void main(String[] args) {
        int temp = 0;
        out: // label
        for (int i = 0; i < 3; ++i) {
            System.out.println("I am here");
            for (int j = 0; j < 20; ++j) {
                if(temp==0) {
                    System.out.println("j: " + j);
                    if (j == 1) {
                        temp = j;
                        continue out; // goto label "out"
                    }
                }
            }
        }
        System.out.println("temp = " + temp);
    }
}

结果:

I am here // i=0
j: 0
j: 1
I am here // i=1
I am here // i=2
temp = 1

不，没有使用goto，但是您可以定义标签并留下一个到标签的循环。您可以使用break或continue后跟标签。所以你可以跳出多个循环层。看看教程。

因为尽管Java语言不使用它，但JVM字节码使用它。