java 判断class类型的几种方式

package other;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;

public class JudgeClass {
	
	public class F
	{
		
	}
	
	public class S extends F
	{
		
	}
	
    /// 通过 instanceof
	@Test
	public void judge1Test() {
		/// 此方法不能判断父子类问题
		F f1 = new F();
		F s1 = new S();
		assertEquals(true, f1 instanceof F);  /// true
		assertEquals(true, s1 instanceof S);  /// true
		assertEquals(true, s1 instanceof F);  /// true
		assertEquals(true, f1 instanceof S);  /// false
	}
	
    /// instanceof 的另外一种写法
	@Test
	public void judge2Test() {
		/// 方法同上
		F f1 = new F();
		F s1 = new S();
		assertEquals(true, f1.getClass().isInstance(f1));  /// true
		assertEquals(true, s1.getClass().isInstance(s1));  /// true
		assertEquals(true, f1.getClass().isInstance(s1));  /// true
		assertEquals(true, s1.getClass().isInstance(f1));  /// false
	}
    /// 通过isAssignableFrom，可以处理父子关系
	@Test
	public void judge3Test() {
		F f1 = new F();
		F s1 = new S();
		assertEquals(true, f1.getClass().isAssignableFrom(F.class));  /// true
		assertEquals(true, s1.getClass().isAssignableFrom(S.class));  /// true
		assertEquals(true, f1.getClass().isAssignableFrom(S.class));  /// true
		assertEquals(true, s1.getClass().isAssignableFrom(F.class));  /// false
	}
	
    /// 通过类名称（不推荐）
	@Test
	public void judge4Test() {
		F f1 = new F();
		F s1 = new S();
		assertEquals("other.JudgeClass$F", f1.getClass().getName());  /// true
		assertEquals("other.JudgeClass$S", s1.getClass().getName());  /// true
	}
    /// 直接比较class，毕竟class也是对象
	@Test
	public void judge5Test() {
		F f1 = new F();
		F s1 = new S();
		assertEquals(true, f1.getClass().equals(F.class));  /// true
		assertEquals(F.class, f1.getClass());  /// true
		assertEquals(S.class, s1.getClass());  /// true
		assertEquals(F.class, s1.getClass());  /// false
	}
}