1、09 p.step(10);1011 A.14 B.20 C.10 D.17正确答案:B解析:2.程序的执行结果是:public class Question private int num; public static void main(String args) Question q = new Question(); q.num=13; update(q); public static void update(Question q) q.num=9;12 A.13 B.9 C.0 D.43.public class Answer int score = 20; Answer ans= n
2、ew Answer(); ans.add(score); main: score = + score); void add(int score) add: score= + score+); A.1add: score=212 score = 21 B. score=20 C. score = 20 D.D解析:4.下列代码编译或运行的结果是:public class Snow public String jump(int x, int y) return jump one; public String jump(int vals) jump two Snow s=new Snow(); ,
3、5); A.public String jump(int vals) 行,编译出错行,抛出运行时异常 C.输出:jump one D.输出:jump twoC解析:5.关于下列代码说法正确的是:public class Storm public void find() public String find() find public double find(int x) return 2.0; A.无编译错误 B.代码 public String find() 行,出现编译错误 C.代码 public double find(int x) 行,出现编译错误 D.代码 return 行处出现编译
4、错误6.请看下列代码:class ClassA class ClassB extends ClassA class ClassC extends ClassA public class Test ClassA p0 = new ClassA(); ClassB p1 = new ClassB(); ClassC p2 = new ClassC(); ClassA p3 = new ClassB(); ClassA p4 = new ClassC(); 13下列选项中放置在处,使程序编译正确的是: A.p0 = p1; B.p1 =p2; C.p2 = p4; D.p2 = (ClassC)p1
5、;A解析:7.下列代码的运行结果是:public class Animal public String noise() Animal Cat cat = null; Animal animal = new Dog(); if (animal instanceof Cat) cat = (Cat) animal; else animal is not Cats instance);141516class Dog extends Animal 1718Dog192021class Cat extends Animal 2223Cat2425 A.Animal B.Dog C.Cat D.anima
6、l is not Cats instance8.请看下列代码编译和运行的结果是:public class Teacher private String name=sun34 Teacher teachers=new Teacher2;5678 A.sun 2 B.null 2 C.null 1 D.运行时抛出NullPointerException异常9.下列代码编译和运行的结果是:class Person String name = public Person(String name) this.name = name;class Employee extends Person String
7、 empNO = 0000 public Employee(String empNO) this.empNO = empNO;public class EmployeeTest Employee e = new Employee(1109 A.输出:0000 B.输出:1109 C.代码public Employee(String empNO) 行,出现编译错误 D.抛出运行时异常10.class A public void start() A Startpublic class B extends A B Start (A) new B().start();A StartB StartA S
8、tart B Start D.编译错误11.public interface A public void doSomething(String thing);interface B interface C extends A, B interface D public void doIt(String thing);class AImpl implements C ,D public void doSomething(String msg) public void doIt(String thing) A.所有类和接口都编译成功 B.接口A编译失败 C.类AImpl编译失败 D.接口C编译失败12.在 Java 中,关于 final 关键字的说法正确的是: A.如果修饰局部变量,必须定义时初始化 B.如果修饰类,则该类只能被一个子类继承 C.如果修饰方法,则该方法不能在子类中被覆盖 D.如果修饰方法,则该方法所在的类不能被继承13.public class Cell private final int id; public Cell(int id) this.id = id; public void updateId(int id) Cell c
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