System.exit()

Examples

Stopping with code 1 when something went wrong. The line Started is never printed:

void main() {
    IO.println("Checking config...");
    boolean configFound = false;
    if (!configFound) {
        IO.println("Config not found");
        System.exit(1);
    }
    IO.println("Started");
}

Output:

Checking config...
Config not found

After System.exit() even the finally block does not run:

void main() {
    try {
        IO.println("in try");
        System.exit(0);
    } finally {
        IO.println("in finally");
    }
}

Output:

in try

Notes

Whoever started the program sees the exit code: in bash it is echo $?, in PowerShell $LASTEXITCODE. Scripts and CI systems use it to tell whether the program succeeded. If main simply finishes, the exit code is 0; on an uncaught exception it is 1. Hooks registered with Runtime.getRuntime().addShutdownHook(...) run before the exit. Libraries and server applications do not call System.exit(): it stops the whole JVM, not just your code.