而(var)!=var[重复]

public static void main(String[] args) {
    double var = Double.NaN;
    System.out.println("var : " + var);
    while (var != var) {
        System.out.println(" I am inside loop now! ");
    }

}

假设这是家庭作业,我会给你一个提示,而不是答案。你需要定义 var 这样地:

double var = // time for you to understand floating point

编辑:为了使这个答案更有用,下面是 Wikipedia's entry on special floating-point values .

双变量=双.NaN

此外,以下内容将导致一个不确定的循环,而不是无限的循环;但是如果主while循环中发生了更多的事情,[我估计]这可能会被认为是有效的无限;认为这是值得发布的,因为这是现实生活中应用服务器上可能发生的事情类型:

public class Puzzle extends Thread {
static boolean keepRunning=true;
static int var=0;



public void run() {

while (keepRunning) {
        var++;
}   

}


public static void main(String[] args) {
    Puzzle p=new Puzzle();
    p.setPriority(Thread.MAX_PRIORITY);
    Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
    p.start();
    System.out.println("Background Thread started");
    try { Thread.sleep(1000); } catch(Exception e) { ; } // Dirty hack to give the background thread chance to start :)
    while (var != var) {
        System.out.println(" I am inside loop now! ");
    }

    keepRunning=false; // we escaped from the loop, switch off the background thread.
}

}