import java.lang.reflect.Constructor;

public class CreateVoid {
    public static void main(String... args) throws Exception {
        //How to get Class by specifying the class name as a character string
        Class<Void> voidClazz1 = (Class<Void>)Class.forName("java.lang.Void");
        Void o1 = getVoid(voidClazz1);

        //How to get the Class from the actual method
        Class<Void> voidClazz2 = (Class<Void>)CreateVoid.class.getMethod("voidMethod", new Class[]{}).getReturnType();
        Void o2 = getVoid(voidClazz2);

        System.out.println(o1);//java.lang.Void@1c6b6478
        //Since the equals method is not overridden, it will always be false if it is another instance.
        System.out.println(o1.equals(o2));//false
        System.out.println(o1.hashCode());//476800120
        System.out.println(o1.toString());//java.lang.Void@1c6b6478
        System.out.println(o1.getClass());//class java.lang.Void
    }

    //If it is void, it will be a primitive type, so Void(=java.lang.Void)is.
    public Void voidMethod(){return null;};

    //Class<Void>Create a Void object from
    private static Void getVoid(Class<Void> voidClazz) throws Exception {
        //Looking into the JDK source`private Void() {}`And the constructor is private so you need to do the following
        //1.Write getDeclaredConstructor instead of getConstructor
        //2.Set the accessible flag to true
        Constructor<?> declaredConstructor = voidClazz.getDeclaredConstructor(new Class[]{});
        declaredConstructor.setAccessible(true);
        return (Void)declaredConstructor.newInstance(new Object[]{});
    }
}

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