Question

我正在测试一个简单的无限递归应用程序，但是我不明白为什么输出有重复的语句而没有换行。仅当我在新线程中的catch块中运行代码时，它才能正常工作。

public class Main{

    private static long count = 0;

    public static void main (String args[]){

        new Main().start();
    }

    public void start(){

        loop();
    }

    public void loop(){

        try{
            loop();

        }catch (StackOverflowError e){

            System.out.println("thread ended (id:" + Thread.currentThread().getId() + ") [count: " +count+"]");
            ++count;
            start();
        }

    }
}

输出：

...
thread ended (id:1) [count: 214]thread ended (id:1) [count: 214]thread ended (id:1) [count: 214]thread ended (id:1) [count: 214]thread ended (id:1) [count: 214]
thread ended (id:1) [count: 215]thread ended (id:1) [count: 215]thread ended (id:1) [count: 215]thread ended (id:1) [count: 215]thread ended (id:1) [count: 215]
thread ended (id:1) [count: 216]thread ended (id:1) [count: 216]thread ended (id:1) [count: 216]thread ended (id:1) [count: 216]thread ended (id:1) [count: 216]
...

重复次数有时会有所不同（每行1条语句）

Answer 1

将try / catch移至start。

public class SO {

    private static long count = 0;

    public static void main(String args[]) {
        new SO().start();
    }

    public void start() {
        try {
            loop();
        } catch (StackOverflowError e) {
            System.out.println("thread ended (id:" + Thread.currentThread().getId() + ") [count: " + count + "]");
            ++count;
            start();
        }
    }

    public void loop() {
        loop();
    }
}

从一个没有展开的调用堆栈的深处调用start是一个坏主意。

输出：

thread ended (id:1) [count: 0]
thread ended (id:1) [count: 1]
thread ended (id:1) [count: 2]
thread ended (id:1) [count: 3]
thread ended (id:1) [count: 4]
thread ended (id:1) [count: 5]
thread ended (id:1) [count: 6]
thread ended (id:1) [count: 7]
thread ended (id:1) [count: 8]
thread ended (id:1) [count: 9]
thread ended (id:1) [count: 10]

为什么会有多条印刷线

1 个答案: