public class Main {  public synchronized void someMethod_1() {    // only one thread can execute here at a time  }
  public void someMethod_11() {    synchronized (this) {      // only one thread can execute here at a time    }  }
  public void someMethod_12() {    // multiple threads can execute here at a time    synchronized (this) {      // only one thread can execute here at a time    }    // multiple threads can execute here at a time  }
  public static synchronized void someMethod_2() {    // only one thread can execute here at a time  }
  public static void someMethod_21() {    synchronized (Main.class) {      // only one thread can execute here at a time    }  }
  public static void someMethod_22() {    // multiple threads can execute here at a time    synchronized (Main.class) {      // only one thread can execute here at a time    }    // multiple threads can execute here at a time  }}