java测试题目.pdf

Q1 Given 1 public abstract class Prod 2 public abstract void prmth1 3 public static void prmth2 4 int mth2 30 5 System out println prmth2 mth2 6 7 public abstract void prmth3 8 What is the result A Compilation succeeds B Compilation fails because of an error on line 1 C Compilation fails because of an error on line 3 D Compilation fails because of an error on line 7 Q2 Given 1 public class ClassA 2 public static void main String args 3 4 switch x 5 default 6 System out println Here it is 7 8 9 The ClassA class can be compiled successfully by inserting one of three possible options on line 3 When inserted separately which three will allow compilation to succeed Choose three A int x 6 B short x 3 C char x y D long x 354 E boolean x true Q3 Given 1 public class NewGarb 2 public static Object getIt 3 Object rg new Integer 3 4 Object dg new Object 1 2 5 dg 0 1 rg 6 dg 0 0 rg 7 rg null 8 return rg 9 10 Which statement is true A The NewGarb class will not compile B The getIt method must not be declared as static C The NewGarb class compiles but receives an exception because dg is not set to null D The rg object is eligible for garbage collection after a call to the getIt method has returned Q4 Given 1 public class SetFor 2 3 public static void main String args 4 5 System out println You will need to use c 6 7 Which two additions will individually allow compilation to succeed Choose two A char c placed on line 2 B char c placed on line 4 C char c f placed on line 2 D char c f placed on line 4 E static char c placed on line 2 F char c new char placed on line 4 Q5 1 public class TeSet 2 public static void main String args 3 int m 2 4 int p 1 5 int t 0 6 for p m 8 m p t 9 10 11 System out println t equals t 12 13 What is the resulting value of t A 2 B 4 C 6 D 7 Q6 1 class IntType 2 public String getType String a int b char c 3 String holdit1 new String 4 holdit1 a 5 return holdit1 6 7 8 9 class OverType extends IntType 10 11 String holdit2 new String 12 holdit2 holdit2 concat This is concat a 13 return holdit2 14 15 16 public static void main String args 17 OverType ot new OverType 18 String x new String x 19 int y 1 20 char z b 21 System out println getType x y z 22 23 When inserted on line 10 which line will override the getType method allowing compilation to succeed and the output This is x A public Text getType String a int b char c B public Text getType int b String a char c C public String getType String a int b char c D public String getType int b String a char c Q7 1 public class MyThread implements Runnable 2 private String holdA This is 3 private int holdB 1 2 3 4 5 6 7 8 9 10 4 5 public static void main String args 6 MyThread z new MyThread 7 new Thread z start 8 new Thread z start 9 10 11 public synchronized void run 12 for int w 0 w 10 w 13 System out println holdA holdB w 14 15 16 What is the result A Compilation fails because of an error on line 6 B Compilation fails because of an error on line 11 C Compilation fails because of errors on lines 7 and 8 D Compilation succeeds and the program prints each value in the holdB array at the end of the This is line Each value is printed two times before the program ends and the values are not printed in sequential order E Compilation succeeds and the program prints each value in the holdB array at the end of the This is line Each value is printed in order from 1 to 10 and after the value 10 prints it starts printing the values 1 to 10 in order again Q8 1 import java awt 2 3 public class Birthdays extends Frame 4 Birthdays 5 super Birthday Reminder 6 String lblsP1 Name Birthday Address 7 String butnsP2 Add Save Exit 8 Panel panelTop new Panel 9 Panel panelBot new Panel 10 panelTop setLayout new GridLayout 3 2 3 3 11 for int x 0 x lblsP1 length x 12 panelTop add new Label lblsP1 x 13 panelTop add new TextField 14 15 for int y 0 y butnsP2 length y 16 panelBot add new Button butnsP2 y 17 18 add panelTop BorderLayout NORTH 19 add panelBot BorderLayout SOUTH 20 21 Which main method should you add to the Birthdays class to allow the program to compile and run with all defined fields properly displayed A public static void main String args Frame visible true B public static void main String args Frame f new Frame f setVisible true C public static void main String args Birthdays b new Birthdays b pack b setVisible true D public static void main String args Frame f Birthdays new Frame f pack f visible true Q9 1 public class GetIt 2 public static void main String args 3 double x 10 2 9 1 8 7 4 int i new int 3 5 for int a 0 a x length a 6 7 System out println i a 8 9 10 The GetIt class should print the following 11 10 9 Which line should you insert on line 6 to accomplish this A i a int Math min x a B i a int Math max x a C i a int Math ceil x a D i a int Math floor x a Q10 Which statement about the Map interface is true A Entries are placed in a Map using the values method B Entries are placed in a Map using the entrySet method C A key value association is added to a Map using the put method D A key value association is added to a Map using the putAll method Answers Q1 Option A is correct because a class must be declared abstract when it contains one or more abstract methods Abstract methods are methods without a body Options B C and D are incorrect because compilation succeeds Q2 Options A B and C are correct because a switch statement test requires an integer expression If the values in the expression are of type byte short or char promotion to the integer value will occur Options D and E are incorrect because class references floating point values and long values are not allowed in the expression Q3 Option D is correct because no accessible references to the object created at line 3 exist after the method returns This is because automatic variables are used for all the references in this code Option A is incorrect because the NewGarb class compiles successfully Option B is incorrect because the getIt method may or may not be declared static Option C is incorrect because an exception is not received Q4 Option D is correct because char c f placed on line 4 will create a local variable which is a variable declared within a method These variables exist only as long as the method exists Option E is correct because static char c placed on line 2 will create a class v ariable which is a variable declared within the class These variables are created and destroyed as the class is created and destroyed Option A is incorrect because it does not use the static keyword A variable that is accessed by a static method must be declared static or the access must be made using an instance reference Likewise option C is not declared static using the static keyword Option B is incorrect because it does not initialize the variable Option F is incorrect because char is not a class and so cannot be instantiated Q5 Option B is correct because t will result in a value of 4 The operator will increment variables by one Stepping through the for loop until p 5 incrementing the variables and performing the calculation will result in t being equal to 4 Q6 Option C is correct because the method name argument list and return type are the same as the getType method defined in the IntType class Overriding methods must be declared with the same name argument list and return type as the overridden method Option A is incorrect because the return type is not the same as the getType method in the IntType class Option B is incorrect because both the return type and argument list are different from the getType method in the IntType class Option D is incorrect because the argument list is different from the getType method in the IntType class Q7 Option E is correct because the Runnable interface is implemented by declaring a synchronized run method The method is declared as synchronized to signify that the object lock must be obtained Options A B and C are incorrect because compilation succeeds Option D is incorrect but would be correct if the run method were not declared as synchronized Q8 Option C is correct because it creates the Birthdays class and dis