如何獲取類實現的所有接口？

Question

在我的測試下面，爲什麼Aa.class.getClasses()返回[]不是[A.class]？畢竟，A是public。

import org.junit.Test; 
import static org.hamcrest.CoreMatchers.is; 
import static org.junit.Assert.assertThat; 

public class GetClassesTest{  

    public interface A {} 
    class Aa implements A {} 

    @Test 
    public void getClassesShouldWork(){ 
     assertThat("should fail, but passes", Aa.class.getClasses(), is(new Class[]{})); 
//  assertThat("should pass, but fails!", Aa.class.getClasses(), is(new Class[]{ A.class })); 
    } 
} 

Answer 1

這是因爲getClasses()返回的類和接口一個類定義不實現。你想要的是Class.getInterfaces()。

import org.junit.Test; 
import static org.hamcrest.CoreMatchers.is; 
import static org.junit.Assert.assertThat; 

public class GetInterfacesTest{  

    public interface A {} 
    class Aa implements A {} 

    @Test 
    public void getInterfacesDoesWork(){ 
     assertThat("should pass, and passes", Aa.class.getInterfaces(), is(new Class[]{A.class})); 
    } 
}