您好，关于java的问题？public boolean equals(Object obj) ？

Question

class BaseClass{public boolean equals(Object obj) {if(getClass() == obj.getClass()) return trueelse return false}}class DerivedClass extends BaseClass {}public class ExerciseCh6_6_2 {public static void main(String[] args){BaseClass b1 = new BaseClass();BaseClass b2 = new BaseClass();DerivedClass d1 =new DerivedClass();//d1생선DerivedClass d2 =new DerivedClass();//d2생선if (b1.equals(d1))System.out.println("derived equals base.");if (d1.equals(b1))System.out.println("base equals derived.");if (b1.equals(b2))System.out.println("base equals base.");if (d1.equals(d2))System.out.println("derived equals derived.");}}结果:base equals base.derived equals derived.怎么得出结果？ 理解不了 谁能解释？谢谢

Answer 1

public final Class<?> getClass()
Returns the runtime class of this Object. The returned Class object is the object that is locked by static synchronized methods of the represented class.
The actual result type is Class<? extends |X|> where |X| is the erasure of the static type of the expression on which getClass is called. For example, no cast is required in this code fragment:

Number n = 0;
Class<? extends Number> c = n.getClass();

Returns:
The Class object that represents the runtime class of this object.
See Also:
The Java Language Specification, Third Edition (15.8.2 Class Literals)
还不理解？看中文翻译
public final Class<?> getClass()返回此 Object 的运行时类。返回的 Class 对象是由所表示类的 static synchronized 方法锁定的对象。
实际结果类型是 Class<? extends |X|>，其中 |X| 表示清除表达式中的静态类型，该表达式调用 getClass。 例如，以下代码片段中不需要强制转换：

Number n = 0;
Class<? extends Number> c = n.getClass();

返回：
表示此对象运行时类的 Class 对象。
另请参见：
The Java Language Specification, Third Edition (15.8.2 Class Literals)

Answer 2

b1和b2是BaseClass 类的两个实例，调用的方法应该是一样的，if语句返回真的话就调用后边的输出语句，后边的d1和d2类同上边的