介绍

JAVA 【引用类型】和【对象类型】在【继承】中的异同。这个问题自己整理过N次。也被人当菜鸟问过N次。所以，在此简单整理一下。以供大家分享。

• 在继承关系中。一般成员变量是依据引用类型
• 在继承关系中。静态成员变量是依据引用类型
• 在继承关系中，一般方法是依据对象类型
• 在继承关系中，静态方法是依据引用类型

注意

静态成员变量，静态方法是基于类的，本文为了測试观察。所以。会用对象去引用静态成员变量和静态方法。

Super Class:

package shuai.study.inherit;public class SuperClass {public String commonString = "SuperClass Common String";public static String staticString = "SuperClass Static String";public int otherCommonInt = 0;public static int otherStaticInt = 10;public void commonMethod() {System.out.println("SuperClass Common Method: " + commonString);}public static void staticMethod() {System.out.println("SuperClass Static Method: " + staticString);}public void otherCommonMethod() {System.out.println("SuperClass Other Common Method: " + otherCommonInt);}public static void otherStaticMethod() {System.out.println("SuperClass Other Static Method: " + otherStaticInt);}
}

Suber Class:

package shuai.study.inherit;public class SuberClass extends SuperClass {public String commonString = "SuberClass Common String";public static String staticString = "SuberClass Static String";@Overridepublic void commonMethod() {System.out.println("SuberClass Common Method: " + commonString);}public static void staticMethod() {System.out.println("SuberClass Static Method: " + staticString);}
}

Test Class:

package shuai.study.inherit;public class Test {public static void main(String[] args) {SuperClass superClass = new SuberClass();// Common member variable is according to quote typeSystem.out.println(superClass.commonString);// Static member variable is according to quote type// Generally we invoke static member as SuperClass.staticString, because static method & variable is based on classSystem.out.println(superClass.staticString);// Common method is according to object typesuperClass.commonMethod();// Static method is according to quote type// Generally we invoke static method as SuperClass.staticMethod(), because static method & variable is based on classsuperClass.staticMethod();System.out.println("==================================================");SuberClass suberClass = new SuberClass();// Inherit member variable from super classSystem.out.println(suberClass.otherCommonInt);System.out.println(SuberClass.otherStaticInt);// Inherit method from super classsuberClass.otherCommonMethod();SuberClass.otherStaticMethod();// Self methodsuberClass.commonMethod();SuberClass.staticMethod();}}

Output:

SuperClass Common String
SuperClass Static String
SuberClass Common Method: SuberClass Common String
SuperClass Static Method: SuperClass Static String
==================================================
0
10
SuperClass Other Common Method: 0
SuperClass Other Static Method: 10
SuberClass Common Method: SuberClass Common String
SuberClass Static Method: SuberClass Static String