• 2022-06-07
    下列关于Test类的定义代码中,正确的是______。
    A: class Test implements Runnable { public void run() {} public void someMethod() {} }
    B: class Test implements Runnable { public void run(); }
    C: class Test implements Runnable { public void someMethod(); }
    D: class Test implements Runnable { public void someMethod() {} }
  • A

    举一反三

    内容

    • 0

      已知有如下定义:package cn.edu.ncu.chenyi;public interface Runnable{public void run();}package cn.edu.ncu.chenyi;public abstract class Animal implements Runnable{public void run();}关于上述两个代码说法正确的是? A: Animal编译失败,因为Animal类实现接口,不能定义为抽象类 B: Animal编译失败,因为Animal类实现接口Runnable,方法run的方法不是抽象方法,方法体不能为空; C: Animal编译失败,需要在方法run中增加修饰符abstract才能修改正确,形如:package cn.edu.ncu.chenyi;public abstract class Animal implements Runnable{ public abstract void run();} D: Animal编译成功,代码正确; E: 以上说法均不正确

    • 1

      下列类的定义中哪些是合法的抽象类?( ) A: sealed abstract class c1{abstract public void test() {} B: abstract sealed public viud test(); C: abstract class c1 { abstract void test(); //test()默认为私有,不合法 D: abstract class c1 {abstract public void test(); }

    • 2

      给定代码如下: public abstract interface Frobnicate { public void twiddle(String s); } 以下哪个类是正确的?(). A: public abstract class Frob implements Frobnicate { public abstract void twiddle(String s) { } } B: public abstract class Frob implements Frobnicate { } C: public class Frob extends Frobnicate { public void twiddle(Integer i) { } } D: public class Frob implements Frobnicate { public void twiddle(Integer i) { } }

    • 3

      interface A{ void x(); } class B implements A{ public void x(){} public void y(){} } class C extends B{ public void x(){System.out.println("C");} } public class Test{ public static void main(String args[]){ B b=new B(); B c=new C(); b.x(); c.y(); } } A: 程序运行错误 B: 程序没有输出结果 C: 程序输出C。 D: class B implements A 编译错误 E: c.y();编译错误

    • 4

      Given: 1. public class Foo implements Runnable { 2. public void run (Thread t) { 3. System.out.println("Running."); 4. } 5. public static void main (String[] args) { 6. new Thread (new Foo()).start(); 7. } 8. } What is the result?