How do I spawn enemies with a delay using threads?

Question

Right now I have this:

Thread enemySpawner = new Thread(new Runnable() {
    public void run() {
        if(world.getCurrentState() == gameState.GAME) {
            world.spawnEnemy(x, y);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
});
enemySpawner.start();

It is called in the constructor of my game. For some reason, only one enemy spawns. How do I fix this?

Answer 1

You need to enclose the spawning code in a loop, i.e.

Thread enemySpawner = new Thread(new Runnable() {
    public void run() {
        while(world.getCurrentState() == gameState.GAME) { // Just changed it to a while loop
            world.spawnEnemy(x, y);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
});
enemySpawner.start();

Threads don't run over and over again; you have to implement the loop logic yourself.