public class OverrideAndOverload { public static void main(String[] args){ Super obj = new Sub(); //向上造型 Goo goo = new Goo(); goo.g(obj); } } class Super{ public void f(){ System.out.println("super.f()"); } } class Sub extends Super{ public void f(){ //方法重写 Sy...
证明: 1classSuper{2publicSuper(){3System.out.println("我是父类super");4}5}6classSubextendsSuper{7publicSub(){8System.out.println("我是子类sub");9}10}11publicclassInstanceDemo {12publicstaticvoidmain(String[] args) {13newSub();14/**15* 我是父类super16* 我是子类sub17*18* 先打印的...
classSup{publicint x,y;Sup(int a,int b){x=a;y=b;}publicvoiddisplay(){int z;z=x+y;System.out.println("add="+z);}}classSubextendsSup{Sub(int a,int b){super(a,b);}publicvoiddisplay(){int z;z=x*y;System.out.println("product="+z);}}//diaplay()在编译时不能被系统识别,...
classSuperClass{privateint n;SuperClass(){System.out.println("SuperClass()");}SuperClass(int n){System.out.println("SuperClass(int n)");this.n=n;}}classSubClassextendsSuperClass{privateint n;SubClass(){super(300);System.out.println("SubClass");}publicSubClass(int n){System.out.println("...
} } class Sub extends Base{ public int method() { //非法,返回类型不一致 return 0; } } Java编译器首先判断Sub类的method()方法与Base类的method()方法的参数签名,由于两者一致, Java编译器认为Sub类的method()方法试图覆盖父类的方法,既然如此,Sub类的method()方法就必须和被覆盖的方法具有相同的返回...
答:类的重用:重复使用已有的类2.UML中类的继承怎么表示?继承的关键词是:extends父类(super class)和子类(sub class)3.继承的语法规则是什么?父类中的属性和方法可以被继承,但是是有条件的;到底能不能继承,主要看访问控制符private、默认、protected、public。4.访问控制符的使用规则是什么?访...
public class Animal { public void move() { System.out.println("动物在移动"); } } public class Dog extends Animal { @Override public void move() { System.out.println("狗在奔跑"); } } public class Test { public static void main(String[] args) { Animal animal = new Animal(); ...
}publicclassTestDog{publicstaticvoidmain(String args[]){Animala=newAnimal();// Animal 对象Animalb=newDog();// Dog 对象a.move();// 执行 Animal 类的方法b.move();//执行 Dog 类的方法} } 这种子类包含与父类同名方法的现象被称为方法重写( Override ),也被称为方法覆盖。可以说子类重写了父类...
The class was enhanced in JDK 1.2 to include a new method, , which supports the removal of entries from the . The class was not updated to override this new method. This oversight allowed an attacker to bypass the check enforced in , and to delete mappings by simply invoking the method....
//Cannot override the final method from SuperClass /*public final void method3() { System.out.println("SubClass Method3"); }*/ publicstaticvoidmain(String[] args) { SuperClass sc =newSubClass(); System.out.println("i = " + sc.i); ...