package java.lang;/** * The {@code Void} class is an uninstantiable placeholder class to hold a * reference to the {@code Class} object representing the Java keyword * void. * * @author  unascribed * @since   JDK1.1 */public finalclass Void {    /**     * The {@code Class} object representing the pseudo-type corresponding to     * the keyword {@code void}.     */    @SuppressWarnings("unchecked")    public static final Class
    
      TYPE = (Class
     
      ) Class.getPrimitiveClass("void");    /*     * The Void class cannot be instantiated.     */    private Void() {}}
     
    

Class
     clazz = Class.forName("jdk.number.integer.Test01");	    Method method = clazz.getMethod("testMethod", null);	    Class
     clazzRT = method.getReturnType();	    System.out.println(clazzRT == Void.TYPE);

返回值是Void，这是一个占位符不能被实例化 ，大多数用来判断方法的返回值是不是空的