Java考试题1

Part 1: Single-choice questions（15 points）1.The constructor of a class that adheres to the Singleton design pattern musthave _____ visibility.A. privateB. protectedC. packageD. public2.Which method is used to define the execution body of a thread?A. start()B. init()C. run()D. main()3.Which modifier should be applied to a method for the lock of the object this to be obtained prior to executing any of the method body?A. finalB. staticC. abstractD. protectedE. synchronized4. A Button is positioned in a Frame. Its size is not affected whenthe Frame is resized. Which layout manager should be used?A. FlowLayoutB. North and South of BorderLayoutC. East and West of BorderLayoutD. GridLayout5.Given the following code:1) class Example{2) String str;3) public Example(){4) str= "example";5) }6) public Example(String s){7) str=s;8) }9) }10) class Demo extends Example{11) }12) public class Test{13) public void f () {14) Example ex = new Example("Good");15) Demo d = new Demo("Good");16) }Which line will cause an error?A. line 3B. line 6C. line 10D. line 14E. line 156.What would be the result of attempting to compile and run the following piece of code?public class Test {public int x;public static void main(String args[]){System.out.println("Value is " + x);}}A. The output "Value is 0" is printed.B. Non-static variable x cannot be referenced from a static context..C. An "illegal array declaration syntax" compiler error occurs.D. A "possible reference before assignment" compiler error occurs.E. An object of type ArrayIndexOutOfBoundsException is thrown.7. You need to create a class that will store a unique object elements.You do not need to sort these elements but they must be unique. What interface might be most suitable to meet this need?A. SetB. ListC. MapD. Vector8. You have these files in the same directory. What will happen when you attempt to compile and run Class1.java//Base.javapackage Base;class Base{protected void amethod(){System.out.println("amethod");}}//Class1.javapackage Class1;public class Class1 extends Base{public static void main(String argv[]){Base b = new Base();b.amethod();}}A. Compile Error: Methods in Base not foundB. Compile Error: Unable to access protected method in base classC. Compilation followed by the output "amethod"D. Compile error: Class1 can not find class Base9.In which of the following ways can items be added to a collection implemented by java.util.ArrayList?I .Items can be inserted at the beginning of the collection.II .Items can be inserted between two existing items in the collection.III .Items can be appended to the end of the collection.A. I, II, and IIIB. I and III onlyC. I onlyD. III only10. Assuming any exception handling has been set up, which of the following will create an instance of the RandomAccessFile classA. RandomAccessFile raf=new RandomAccessFile("myfile.txt","rw");B. RandomAccessFile raf=new RandomAccessFile( newDataInputStream());C. RandomAccessFile raf=new RandomAccessFile("myfile.txt");D. RandomAccessFile raf=new RandomAccessFile(new File("myfile.txt")); 11．Given the following command to run a correct class: java MyTest a b cWhich statements are true?A. args[0] = "MyTest a b c"B. args[0] = "MyTest"C. args[0] = "a"D. args[1]= 'b'12．Which of the following statements are true about a variable created with the static modifier?A.Once assigned the value of a static variable may not be alteredB. A static variable created in a method will keep the same value between callsC. Only one instance of a static variable will exist for any amount of class instancesD. The static modifier can only be applied to a primitive value13.Which of the following statements are true?A.The elements in a Java array can only be of primitive types, not objectsB. Arrays are initialized to default values wherever they are createdC. An array may be dynamically resized using the setSize methodD. You can find out the size of an array using the size method14. A design pattern is typically used toA. allow the use of object-orientated concepts in a language that is not object-orientedB. describe a practical solution to a common design problemC. ensure that code executes at optimal speed during runtimeD. reduce the number of classes in the design of a program15. Which of the following is a Java event that is generated when a JButton component is pressed?A. ClickEventB. WindowEventC. ActionEventD. ButtonEventPart 2: Multi-choice questions（30 points）1. What might cause the current thread to stop executing.A. An InterruptedException is thrown.B. The thread executes a wait() call.C. The thread constructs a new Thread.D. A thread of higher priority becomes ready.2. Which of the following method can be used to define a new thread class?A. implement the Runnable interfaceB. add a run() method in the classC. create an instance of ThreadD. extend the Thread class3. Given the following method body://you add code here{if (sometest()) {unsafe();}else {safe();}}The method "unsafe" might throw an IOException (which is not a subclass of RunTimeException). Which correctly completes the method of declaration when added at line one?A. public void methodName() throws ExceptionB. public void methodname()C. public void methodName() throw IOExceptionD. public void methodName() throws IOExceptionE. public IOException methodName()4.Which classes are used to implement TCP/IP client and servers?A. ServerSocketB. ServerC. SocketD. DatagramPacketE. DatagramSocket5. Which of the following event listeners have event adapters defined in Java?A. MouseListenerB. KeyListenerC. ActionListenerD. ItemListenerE. WindowListener6. Which statements of the event listener are true?A. Multiple listeners can be attached to one component.B. Only one listener can be attached to one component.C. One listener can receive and process the events from multiple components.D. One listener can receive and process the events from only one component.7.Which of the following can be parts of the Java source file Calculation1.java?A. public class Calculation1{//...}B. import java.io.*;C. package myPackage;D. import java.awt.*;E. static class Arg{//...}F. class Calcu{//...}G. public class Calculation2{//...}8. public void fun (){int i;try{i=System.in.read ();System.out.println("Location 1");} catch (IOException e) {System.out.println("Location 2");} finally {System.out.println("Location 3");}System.out.println("Location 4");}If an IOException occurs, what will be printed?A. Location 1B. Location 2C. Location 3D. Location 49. The Person, Student and Teacher are class names. These classes have the following inheritance relation : Student and Teacher extend Person. In Java source file a specific method has an argument. In order to handle all these classes in this method which type of argument of this method should be used?A. PersonB. StudentC. TeacherD. ObjectE. None of them can be used.10.Which statements are correct?A. In Java single inheritance is allowed, which makes code more reliable.B. A subclass inherits all methods ( including the constructor ) from the superclass.C. A class can implement as many interfaces as needed.D. When a class implements an interface, it can define as many methods of the interface as needed.11. Consider the following code:Integer s = new Integer(9);Integer t = new Integer(9);Long u = new Long(9);Which test would return true?A. (s==u)B. (s==t)C. (s.equals(t))D. (s.equals(9))E. (s.equals(new Integer(9))12. Which of the following statements are true?A. If a class has any abstract methods it must be declared abstract itself.B. All methods in an abstract class must be declared as abstractC. When applied to a class, the final modifier means it cannot be sub-classedD. An interface cannot be instantiated13. Which of the following statements are true?A. The default constructor has a return type of voidB. The default constructor takes a parameter of voidC. The default constructor takes no parametersD. The default constructor is not created if the class has any constructors of its own.14. Which methods are correct overloading methods of the following method:public void example(){...}A. public void example( int m){...}B. public int example(){...}C. public void example2(){...}D. public int example ( int m, float f){...}15. Which one of the following is correct to create an array?A. float f[][] = new float[6][6];B. float f[][] = new float[][6];C. float [][]f = new float[6][6];D. float [][]f = new float[6][];Part 3: Read Programs（15 points）Please reading the following program carefully, give the correct answer and explain why.1. (7 points)public class Exam1 {public static int counter;static{System.out.println("Static " + counter);counter = 10;}public static int getTotalCount() {return counter;}public int getCount() {return counter;}public Exam1() {counter += 10;System.out.println("Constructor "+counter);}public static void main(String[] args) {System.out.println("Number of counter is " +Exam1.getTotalCount());Exam1 count1 = new Exam1();System.out.println("getCounter " + count1.getCount());Exam1 count2 = new Exam1();count2.counter++;System.out.println("getTotalCount " + count2.getTotalCount()); }}2. (8 points)//class Animalclass Animal {private String type;public Animal() {type = "An Animal";System.out.println("Type: "+ type);}public Animal(String aType) {type = new String(aType);System.out.println("Type: "+ type);}public String toString() {return "This is a " + type;}}//class Dogclass Dog extends Animal {private String name;private String breed;public Dog(String aName) {super("Dog");name = aName;breed = "Unknown";}public Dog(String aName, String aBreed) {name = aName;breed = aBreed;}public String toString() {return super.toString()+ "," + this.breed;}}//class Exam2public class Exam2 {public static void main(String[] args) {Dog aDog = new Dog("Fido", "Chihuahua");Animal animal = new Dog("Lassie");System.out.println(aDog.toString());System.out.println(animal.toString());}}Part 4: Programming（40 points）1（30 points）Please design an application based on the following specifications:a) Class Person has 2 attributes: id and nameb) Class Project models project, has 3 basic attributes:projectID , projectName ,startDate.c) Class ProjectTask models a engineer’s task of a project,has 3 basic attributes: engineerID, engineerName, engineerT askd) A Engineer is a Persone) A Engineer can take many projectsf) A projcet contains many engineers tasks (Tips: cantains aattribute which type is ArrayList<ProjectTask>)g) The tasks of all engineers in a project exist in a Plain Text File,the format of each task is:“engineerID_engineerName_engineerTask”,for example, “0318_zhang_module3”.h) Project project1’s tasks file name is “project1.txt” , Projectproject2’s tasks file name is “project2.txt”,and so on.Here is what you should do:1) Draw the UML Class Diagram according the specifications2) Complete the following Classes in Java:Person , Engineer, ProjectTask , Project3) Define a method in class Project for reading the tasks of eachproject from specified file name, and save them in Arraylist<ProjectTask> tasks. using java.util.StringTokenizer to getengineerID, engineerName, engineerT askThe signature of this method is:public void getTasks(String aProjectTasksFile)4) Design a GUI Class in Java, using BorderLayout, the left is thelist of all Project Name, the right is a TextArea.5) Complete the following event processing inner Class in Java,When user selects a Project Name, show all tasks of the project in the TextArea, each line will be a task of a engineer.class InnerDisplayListener implementsListSelectionListener{ public void valueChanged(ListSelectionEvent event) { //you code here}}。