1.Which is the basic unit of a java program?（B ）

1. Java方法          B、Java类
2. Java变量          D、以上都是

2.Let null be the value of a variable a，please select the possible type of （B ）

1. Integer            B、String
2. System            D、都有可能

3.Which of the following class is correct？（ D）

1. public class Bean{}
2. public class Circle{

     double r；

     r==0.0；

     }

1. public class Point{

     public point(){}

     }

1. 都正确

4.Given Word w=new Word(“Java”).Please select the proper constructor（ C）

1. public word(){}            B、public word(String w){}
2. public Word(String w){}     D、public void Word(String W){}

5.Which of the following privilege has the

1. 私有访问权限 private          B、默认访问权限default
2. 受保护的访问权限   protected     D、公共访问权限public

6.Let int[] data={3,8,12,6},the value of data[2] is （C ）

  A、3            B、8            C、12            D、6

7.Given Person p=new Student().We can conclude that（ D）

1. Person类的父亲是Object类
2. Student类的父亲是Object类
3. Student类是Person类的直接子类或者间接子类
4. 都正确

8.Which of the following option is correct?（B ）

1. int[] data=new int[0];
2. String[] lines=new String[5];
3. String[] person={};
4. 都正确

9.Please select a proper class with belongs to the package java.lang（ D）

1. System          B、Object          C、Integer          D、都属于

10.Let Paper be a class extending from Document and d be a variable of type Document,when running Paper paper=(Paper)d,the possible exception may be thrown is（B ）B

1. NullPointerException              B、ClassCastException
2. IOException                     D、都有可能

1. How many new objects are constructed when running String[] persons=new String[3]？（ A）

  A、1            B、2            C、3            D、4

12.The keyword declaring a subclass is （C）C

1. Object                       B、public

C. extends                       D、implements

13. Given the following program. The correct statement is （ D）

Public class Address{

Private String city;

Private String zipcode;

Public Address(String zip){}

}

A、Address addr = new this();               B、Address addr = new Address();

C、Address addr = new this(“210000”);        D、Address addr = new Address(“210000”);

14.Consider the following program, which is correct?（ D）

 Public class Test{

Public static void main(String[] args){

String name;

String hello = “Hello,” + name；

System.out.println(hello);

}

}

A、程序运行输出结果为Hello     B、程序运行结果为Hello, null

C、程序运行产生空指针异常      D、程序存在语法错误无法运行

15.Given Document doc = new News（ ）.We can conclude the option（ ） must be wrong（A）

A、 New d = doc;                B、New d = (News)doc;

C、Document d = doc;             D、Document d = (News)doc;

16.在Paper类中覆盖equals方法的正确形式是（ C）

A、public boolean equals()               B、public Boolean

C、public Boolean equals(paper obj)        D、都正确

17.The parent class of FileNotFoundExceptions is （B ）

1. Exception                      B、IOException

C、RuntimeException               D、ClassNotFoundException

18.Let Person be a java class and variables a and b be of type Person. Which option is syntactically(语法上) invalid in any case?（D ）

A、Boolean ok = a==b                    B、boolean ok = a.equals(b);

C、boolean ok = a instance of Person;       D、boolean ok = a>b;

19.Which of the following statement is true?（A ）

A、static variable are shared by all the instances of the class.

B、static methods are tied to a specific object.

C、static constants are final variables and tied to a specific object

D、The static modifier can only be used to declare static variables.

1. 运行下面程序最可能的输出的结果是（ D）

Import java.util;

Public class Test{

   Public static void main(String[] args){

      ArrayList list = new ArrayList();

      list.add(“John”);

      list.add(3);

      list.add(null);

      list.add(null);

      System.out.println(list);

}

}

A、0x38dd             B、[John,3]

C、[John,3,null]         D、[John,3,null,null]

21.Whcih is the basic environment for developing java program?（C ）

A、Eclipse      B、NetBeans      C、JDK      D、JRE

22.boolean is a wrapper class declared in the package（ B）

A、java.io       B、java.lang

C、java.net      D、java.util

23.Which class is used to read a text file?（ D）

A、Reader   B、FileReader   C、InputStream   D、FileInputStream

24.Let variable a be a member of class Point, the possible type（ D）

A、int    B、double    C、Point    D、Any of the above

25.Which the following method is correct?（C ）

A、 public void next(){return null;}

B、public int next(){return null;}

C、public int[] next(){return null;}

D、public int[] next(){return {2,3};}  

26.Given int a=b.length .Please select a proper type for b.（ C）

A、String      B、int      C、int[]      D、Integer

27.Given Person as follows.Please add a constructor from the following option（ D）

Public class Person{

Private int age;

Private String name;

Public Person(int age, String name){}

}

A、Public Person(){this();}

B、Public Person(int age){this(age);}

C、Public Person(String name){this(name);}

D、Public Person(Person copy){this(copy.age,,copy.name);}

28.Considering the following code, which is correct?（ C）

Public class Person{

Static int[] arr = new int[5];

Public static void main(String[] args){System.out.println(arr[0]);}

}

A、Cannot be compiled        B、Can be compiled but cannot run

C、Output 0                 D、Output null

29.Given the program as follows.How many properties have a Student object?（D ）

Class Person{

Private int age;

Private String name;

}

Class Student extends Person{

Private String school;

}

A、0            B、1            C、2            D、3

30.FileInputStream is a class declare in java.io.Please select a proper constructor for it.（C ）

A、Public FileInputStream(String file)

B、Public FileInputStream(String file)throws Exception

C、Public FileInputStream(String file)throws IOException

D、Public FileInputStream(String file)throws FileNotFoundException

31.Given Person[] persons = this.friends(). We can conclude the proper form of friends must be（D ）

A、void friends()            B、String friends()

C、Person friends()          D、Person[] friends()

1. Which of the following statement is wrong in any case？（ B）

1. return this                  B、return this();
2. return this.age;              D、return this.toString();

33.Given Student extends Person{}. The person class of Student is（ B）

A、Object        B、Person        C、Student        D、Nothing

34.（Continue with 33）By declare Student a = b; the type of variable b must be（ C）

A、Object        B、Person        C、Student        D.、Any of the above

35.Given Report as follows. Please select a valid return statement for makeInfo（ A）

Public class Report{

Private String title = “Unknown”

Private static String makeInfo(){         ;}

}静态方法不能对非静态变量进行引用

A、return new Report().title   B、return title    C、return this.title     D、都正确

36.Given String[] persons = {“Hello”, “World”}. Which statement is correct?(AB)

A、persons = new String[10];        B、persons[0] = “John”;

C、persons[2] = “Marry”;             D、都正确

37.Which is wrong about Java class?（C ）

A、each Java class contains toString() methond

B、each Java class is a direct or indirect subclass of Object

C、each Java class could act as a superclass to derive subclass

D、each Java class is a date type

38.Given a statement n = new News(), where News is a subclass of Document.We can conclude that the type of n is（ D）

A、Object        B、Document        C、News        D、都可能

39. Given a statement Document doc = new Paper().where Document is an abstract class. Wecan conclude that（ A）

A、Paper must be a concrete class

B、Paper must be the direct subclass of Document

C、The statement Paper obj = new Paper() must be invalid

D、The statement Object obj = new Paper() must be invalid

40.Please select a correct option（D ）

A、Exception e = new Exception();              

B、Object obj = new NullPointerException();

C、RuntimeException e = new RuntimeException();

D、都正确

辨析题

YES1.Java程序只有8种简单的数据类型，java.lang包含为每种简单数据类型申明了一个对应的引用数据类型，我们把这些引用数据类型称为封装类。

NO2.根据语句 Point p = new Point);可知Point类至少显式申明了一个构造方法。

YES3.使用BuferedReader可以用一行字符串一行字符串的方式读取输入内容。

YES4. URL类是java.net包内中明的预定义类，我们可以用它来读取网络中HTML页面文件

的内容。

NO5.根据语句Record[] data = new Record[10];可以断定Record一定是具体类。在java.lang里面的抽象类

YES6.任何一个Java类都至少有一个构造方法。

NO7.由Exception维承的任何自定义类都属于告运行时异常。

YES8.开发Java程序的 般过程是先编写源程序，保存在后级名为java的文件中，然后编译源程序，检查程序语法上是否正确，并翻译成后缀名为class的字节码文件，最后加载、

解释执行字节码文件。

NO9.根据中明public abstract class Circle extend Shape{}可知Shape类一定是抽象类。

YES10.己知a, b均为Point类型的变量并且a.equals(b)的值为true.那么我们可以判断Point类一定覆盖了equals方法。

二、请改正下面程序中的语法错误。（共2小题，每题3分，共计6分）

1、 public class NamedBean{

int id;

String name;

public NamedBean(String name){

this(1,name);

}

public NameBean(int id,String name){

this.id = id;

this.name = name;}

}

2、 class MoneyException extends Exception{}

class Money {

public static int parse(String txt)throws MoneyException {return 0;}

}

class Test{

public static void main(String[] args) throws MoneyException{

String txt=”三万八千元”

System.out.println(Money.parse(txt));

}

}

3、 abstract class Human{

String name = “Unknown”;

public Human(String name)

{

this.name = name;

}

}

class Boy extends Human{

public Boy(String name){

super(name);

}

}

4、 import java.io.*;

class Test{

public static void main(String[] args) throws IOException {

FileReader reader = new FileReader(“sample.txt”);

int c = reader.read();

while(c != -1){

System.out,println((char)c);

C = reader.read();

}

Reader.close();

}

}

程序分析题（共8小题，每题5分，共计40分）

Reading Program One and then answer questions 1-3

1. What is the out put when running this program?

Product:iPhone Price:1000.0元

1. Please present the members declared in class Product , including constructors.

price,name,Product(String n),getinfo()

1. Please illustrate the detailed process of constructing the Product object. 请说明构建Product对象的详细过程。

检测类是否被加载（常量池）

在堆上为对象分配内存

为分配的内存空间初始化零值：

对对象设置hashcode、所属的类

执行 init 方法

Reading Program Two and then answer questions 4-6

1. What is the output when running the program?

(10,10)

1. Please point out the application of method override. 请指出方法重写的应用。

当子类需要父类的功能，而功能的主体子类还有自己特有的内容时，可以重写父类中的方法，这样，即沿袭了父类的功能，又定义了子类自己特有的内容。

1. Polymorphism is one of the important characters of object-oriented programming . Please point out how the program applies the character. 多态性是面向对象编程的重要特征之一。请指出程序如何应用该特征。

向下转型，将父类对象的引用强转成子类类型，使用子类特有的方法。大大提高程序的可拓展性。

Reading Program Three and then answer questions 7-8

1. What is the output when running the program?

南京

扬州

镇江的周边城市有：南京扬州

1. 当main方法执行完第5条语句后，请画出此时内存中程序运行的栈堆结构状态并做简要说明.

Program one

public class Product{

private double price = 1000;

private String name = “UNKNOWN”;

public Product (String n){ name = n;}

public String getinfo(){ return = “Product:” + name + “\tPrice:” + price + “元”;}

}

class Test{

Product p = new Product(“iPhone”);

System.out.println(p.getinfo());

}

Program two

class Point{

protected int x,y;

public Point(int x, int y){ this.x = x;this.y = y;}

public String getinfo(){ return “(“ + x + “,” + y + “)”;}

}

class Point3D extends Point{

private int z;

public Point3D(int x,int y,int z){

super(x,y);   this.z = z;

}

public String getinfo(){return “(“ + x + “,” + y + “,” + z + “)”;}

}

class Test{

public static void main(String[] args){

Point p1 = new Point(10,10);

System.out.println(p1.getinfo());

}

Program Three

class City{

private String name;

private City[] neighbours = {};

public City(String name){ this.name = name;}

public void addNeighbour(City city){

int len = neighbours.length;

City[] temp = new City[len + 1];

for(int i = 0;i < len;i++) temp[i] = neighbours[i];

temp[len] = city;

neighbours = temp;

}

public String toString(){

if(neighbours.length == 0) return name;

String info = name + “的周边城市有：”;

for(){

info += neighbours[i].name;

}

return info;

}

}

public class Test{

public static void main(String[] args){

City c1 = new City(“南京”);

City c2 = new City(“扬州”);

City c3 = new City(“镇江”);

c3.addNeighbour(c1);

c3.addNeighbour(c2);

System.out.println(c1);

System.out.println(c2);

System.out.println(c3);

}

}

Reading Program One and then answer questions 1-3

1. What is the output when running the program?
2. Please present the members declared in class Node,including constructors.
3. Please illustrate the detailed process of constructing the Node object.

Reading Program Two and then answer questions 4-6

1. What is the output when running the program?

2012-4-22

2012-4-10

    2012-4-10

1. Please in terms of the program explain the main usage of the keyword this.

This()指向本类相应的构造方法，”this.”为指向本对象中的成员变量

1. 请使用方法调用栈详细说明date2.setDay(10)语句的执行过程

1. 把形参10压入栈中
2. 调用方法setDay，把this.day压入栈中，引用堆中对象date2中的day变量
3. 通过this.day把对象中的day重新赋值为10
4. 依次释放栈中的this.day和setDay

Reading Program Three and then answer questions 7-8

1. What is the output when running the program?

id:100

Bean:Java Programming id:200

Bean:Java Programming id:300

Bean:Java Programming id:300

1. Polymorphism is one of the important characters of object-oriented programming point out how the program applies the character.

向下转型，将父类对象的引用强转成子类类型，使用子类特有的方法。大大提高程序的可拓展性。

Program one

public class Node{

private int id;

private String label = “UNKNOWN”;

public Node(String label){this.label = label;}

public String getinfo(){ return “Node:” + id + “\tLabel:” + label;}

}

Program two

class MyDate{

private int day;

private int month;

private int year;

public MyDate() {this(1,1,1960);}

public MyDate(int d,int m,int y){day = d;month = m;year = y;}

public void setDay(int day){this.day = day}

public String getinfo(){return year + “-“ + month + “-“ day;}

}

public class Test{

public static void main(String[] args){

MyDate date1 = new MyDate(22,4,2012);

System.out.println(date1.getinfo());

MyDate date2 = date1;

date2.setDay(10);

System.out,println(date1.getinfo());

System.out,println(date2.getinfo());

}

}

Program three

class Bean{

protected int id;

public Bean(int id){

this.id = id;

}

public String toString(){

return “id:” + id;

}

}

class NamesBean extends Bean{

private String name;

public NamedBean(int id,String name){

this.id =id;

this.name = name;

}

public String toString(){

return “Bean:” + name + “\t” + super.toString();

}

}

public class Test{

public static void main(String[] args){

Bean bean_1 = new Bean(100);

System.out.println(bean_1);

Bean bean_2 = new NamedBean(200,”Java Programming”);

System.out,println(bean_2);

bean_1 = bean_2;

bean_1.id = 300;

System.out.println(bean_1);

System.out,println(bean_2);

}

}

程序设计题（共3小题，每题8分，共计24分）

1. Given class Test as follows.Please complete the program such that it can correctly and output the result as follows.

John’s friend is Mary

Mary’s friend is John

class Person{

String name;

Person friend=null;

public Person(String name) {

this.name = name;

}

void setFriend(Person person) {

this.friend = person;

if(person.friend==null) person.friend=this;

}

String getinfo() {

return name + "'s friend is " + friend.name;

}

}

public class Test{

public static void main(String[] args){

Person john = new Person(“John”);

Person mary = new Person(“Mary”);

john.setFriend(mary);

System.out.println(john.getinfo());

System.out.printlb(mary.grtinfo());

}

}

1. Given an abstract class Sltape and a test class Test as follows.Please complete the subclass of Shape such that it can run correctly and output the result as follows.

r的面积是：100.0

c的面积是：314.1592653589793

class RectangleShape extends Shape{

double length,width;

public double getArea() {

return length*width;

}

}

class CircleShape extends Shape{

double radius;

public double getArea() {

return radius*radius*Math.PI;

}

}

abstract class Shape{

public abstract double getArea();

}

public class Test{

public static void main(String[] args){

RectangleShape r = new RectangleShap();

r.length = 10;r.width = 10;

System.out,println(“r的面积是:” + r.getArea());

CircleShape c = new CircleShape();

c.radius = 10;

System.out.println(“c的面积是：” + c.getArea());

System.out,println(“Point.counter=” + Point.counter);

}

}

1. Given class Test follows.Please complete the program such that it can run correctly and output the result as follows.

[Trump’s:1,eldest:1,son:1,has:1,tested:1,positive:1,for:1,the:1,coronavirus:1]

class ArrayList{

Weword[] list = new Weword[9];

int i=0;

int size() {

return i;

}

Weword get(int i){

return list[i];

}

void add(Weword w) {

list[i++]=w;

}

public String toString() {

String ans="[";

for(int j=0;j<i;j++) {

ans+=list[j].word + ":" + list[j].num;

if(j!=i-1) ans+=",";

}

ans+="]";

return ans;

}

}

class Weword{

int num=0;

String word;

Weword(String word){

this.word=word;

}

}

import java.util.*;

public class Test{

private static Weword addTo(Weword w,ArrayList list){

for(int i =0;i < list.size();i==) if(w.equals(list.get(i))) return list.get(i);

list.add(w);

return w;

}

public static void main(String[] args){

String line = “Trump’s eldest son has tested positive for the coronavirus”;

String[] words = line.split(“ “);

ArrayList list = new ArrayList();

for(int i = 0;i < words.length;i++){

Weword w = addTo(new Weword(words[i],list);

w.num++;

}

System.println(list);

}

}

1. Given class Test as follows.Please complete the program such that it can run correctly and output the result as follows.

(10,10)

圆心：（10,10） 半径：18.8

class Point{

int x,y;

Point(int x,int y){

this.x=x;

this.y=y;

}

String getInfo() {

return "（" + x + "," + y + "）";

}

}

class Circle{

Point center;

double r;

Circle(Point center,double r){

this.center=center;

this.r=r;

}

String getInfo() {

return “圆心：（“ + center.x + center.y + "半径：" + r;

}

}

public class Test{

public static void main(Stringp[] args){

Point p = new Point(10,10);

Circle c = new Circle(p,18.8);

System.out.println(c.center.getInfo());

System.out.println(c.getInfo());

}

}

1. Given class Test as follows.Please complete the program such that it can run correctly and output the result as follows.

我是经理张三

我是员工李四

class User{

String name;

String say() {

return null;

}

}

class Manager extends User{

Manager(String name){

this.name = name;

}

String say() {

return "我是经理" + name;

}

}

class Employee extends User{

Employee(String name){

this.name = name;

}

String say() {

return "我是员工" + name;

}

}

public class Test{

public static void main(String[] args){

User[] users = {new Manager(“张三”),new Employee(“李四”)};

for(int i = 0;i < users.length;i++){

System.out.println(users[i].say());

}

}

}

1. Given class Test as follows.Please complete the program such that it can run correctly and output the result as follows.

[Java:12次,NUFE:1次]

class ArrayList{

Word[] words = new Word[100];

int i=0;

boolean contains(Word w) {

for(int j=0;j<i;j++) if(words[j].word.equals(w.word)) return true;

return false;

}

void add(Word w) {

words[i++]=w;

}

public String toString() {

String ans = "[";

for(int j=0;j<i;j++) {

ans+=(words[j].word + ":" + words[j].num + "次");

if(j!=i-1) ans+=",";

}

return ans + "]";

}

}

class Word{

String word;

int num=1;

Word(String word){

this.word=word;

}

}

import java.util.*;

public class Test{

public static void miain(String[] args){

ArrayList list = new ArrayList();

Word[] words = {

new Word(“Java”),

new Word(“NUFE”),

new Word(“Java”)

};

for(int i = 0;i < words.length;i++){

if(list.contains(words[i])) continue;

List.add(words[i]);

}

words[0].num = 122;

System.out,println(list);

}

}