system. Exit (0) and system exit(1)

One 、 sketch

java.lang.System Source code , The method is described as follows ：

/** * Terminates the currently running Java Virtual Machine. The * argument serves as a status code; by convention, a nonzero status * code indicates abnormal termination. * <p> * This method calls the <code>exit</code> method in class * <code>Runtime</code>. This method never returns normally. * <p> * The call <code>System.exit(n)</code> is effectively equivalent to * the call: * <blockquote><pre> * Runtime.getRuntime().exit(n) * </pre></blockquote> * * @param status exit status. * @throws SecurityException * if a security manager exists and its <code>checkExit</code> * method doesn't allow exit with the specified status. * @see java.lang.Runtime#exit(int) */
    public static void exit(int status) {
    
    Runtime.getRuntime().exit(status);
    }

Both are used to end the currently running JVM, Exiting the program means , If status Is a non-zero parameter , Then it means an abnormal exit .

difference ：

1. system.exit(0)： After the normal execution of the program, exit . The method is to stop the content in the whole virtual machine , and dispose() Just close this window , But it didn't stop the whole application exit() . in any case , Memory is free . In other words, even JVM It's all closed , There can't be anything else in memory .

2. system.exit(1)： Abnormal exit , That is, whether the program is executing or not , All quit .1 Or not 0 Indicates abnormal exit procedure . No matter status Why do all values exit the program .return Is to go back to the upper level , and System.exit(status) Is to go back to the top .

Two 、 usage

stay if-else In judgment , If the program performs as expected , In the end, you need to stop the program , So use System.exit(0). and System.exit(1) Generally placed on catch block in , When an exception is caught , Used to stop the program . This status=1 Is used to indicate that the program exits abnormally .