OCPJP 6 Mock Exam -15

1 . Which of the following can prevent a thread from executing?

  1. A call to its pause method
  2. A call to Thread.yield()
  3. Another thread is given higher priority
  4. A call to its halt() method

2 . Which of the following represent correct syntax for assertions?

  1. assertion(b==false);
  2. assert (b==false);
  3. assert() b==false;
  4. if(b!=true) assert;

3 . What will be the output?

public class Master{
    boolean bContinue=false;
    public static void main(String argv[]){
	Master m = new Master();
	m.go();
    }
    public void go(){
	Slave s = new Slave(this);
	Thread t1 = new Thread(s);
	t1.start();
	while(bContinue==false){
	}
	s.setPrice(200);
    }
}

class Slave implements Runnable{
    int iPrice =100;
    Master master;
    Slave(Master m){
	master=m;
    }
    synchronized public void setPrice(int iM){
	iPrice=iM;
    }

    synchronized public void run(){
	master.bContinue=true;
	while(true){
	    System.out.println(iPrice);
	}

    }
}

Choose the one below:

  1. Compilation but no output as the run method of slave is not correct
  2. Compilation and output of 100 several times followed by 200 several times
  3. Compilation and repeated output of 100
  4. Compile time error, while cannot be given an unconditional boolean value

4 . What will be the output?

public class Tux extends Thread{
	static String sName = "Techno";
	public static void main(String argv[]){
		Tux t = new Tux();
		t.name(sName);
		System.out.println(sName);
	}
	public void name(String sName){
		sName = sName + " park";
		start();
		}
	public void run(){
		for(int i=0;i < 4; i++){
			sName = sName + " " + i;
	        }
	}
 }

Choose the one below:

  1. Compile time error
  2. Compilation and output of “Techno park”
  3. Compilation and output of “Techno park 0 1 2 3″
  4. Compilation and probably output of “Techno” but possible output of “Techno 0 1 2 3″

5 . Which of the following require explicit try/catch exception handling by the programmer?

  1. Traversing each member of an array
  2. Attempting to open a file
  3. Attempting to open a network socket
  4. Accessing a method in other class

6 . What will be the output?

public class RandomExample{
    public static void main(String argv[]){
        int iRand;
        iRand = Math.random();
        System.out.println(iRand);
    }
}

Choose the one below:

  1. Compile time error referring to a cast problem
  2. A random number between 1 and 10
  3. A random number between 0 and 1
  4. A compile time error about random being an unrecognised method

7 . Which of the following statements are true?

  1. The vaue of the Integer class can be changed using the = operator
  2. The value of the Integer class can be changed using the setValue method
  3. The value of the Integer class can be changed using the setInt method
  4. Once assigned the value of an instance of Integer cannot be changed

8 . What will be the output?

import java.util.*;
public class TechnoExample{
    public static void main(String argv[]){
	TechnoExample junk = new TechnoExample();
	junk.sampleMap();
    }
    public void sampleMap(){
	TreeMap tm = new TreeMap();
	tm.put("a","Bill");
	tm.put("b","Kathy");
	tm.put("c","Carl");
	Iterator it = tm.keySet().iterator();
	while(it.hasNext()){
	    System.out.print(tm.get(it.next()));
	}
    }
}

Choose the one below:

  1. Compile time error, a19 cannot be used as a method name
  2. Compilation and output of BillKathyCarl
  3. Compilation and output of BillCarlKathy
  4. Compilation and output of abc

9 . What will be the output?

class Biddy{
    public Biddy(){
	System.out.print(" Biddy ");
    }
}
class Val extends Biddy{
    public Val(){
	System.out.print(" Val ");
    }
}

public class BluePeter extends Val{
    public static void main(String argv[]){
	BluePeter bp = new BluePeter();
	bp.shep(3);
    }
    public void shep(float i){
	System.out.println(i);
    }
}

Choose the one below:

  1. Compilation and output of Val Biddy 3
  2. Compilation and output of Val Biddy 3.0
  3. Compilation and output of Biddy Val 3.0
  4. Compile time error, wrong parameter type passed to method shep

10 . which of the following statements are true of the ArrayList class?

  1. It can store primitive or references as elements
  2. It implements the List interface
  3. It has a get(int index) method which returns the element at the specified position in the list
  4. The elements are ordered but not sorted

11 . What will be the output?

class Base{
    public int iAcres=3;
}
public class Mfields extends Base{
    private int iAcres=3.5;
    public static void main(String args[]){
	Base mf = new Mfields();
	System.out.println(mf.iAcres);
    }
}

Choose the one below:

  1. Compile time error
  2. Compilation and output fo 3.5
  3. Compilation and output of 3
  4. Compilation but no output at runtime

12 . Which of the following statements are true?

  1. A variable declared as public within a method will always be visible from code anywhere else in the class
  2. A variable declared as public at class level will always be visible from code anywhere else in the class
  3. A method with no visibility modifier can be less visible than one declared with the protected modifier
  4. Only one copy will ever exist of a method variable declared as static

13 . Which of the following are valid uses of the assert statement?

  1. assert();
  2. assert {
    int > 0;
    }
  3. assert(iMonth < 12);
  4. assert (iAge = 0);

14 . At what point will the object created on line 8 be eligible for garbage collection?

 public class RJMould{
     StringBuffer sb;
     public static void main(String argv[]){
 	RJMould rjm = new RJMould();
 	rjm.kansas();
    }
     public void kansas(){
 	sb = new StringBuffer("Manchester");
 	StringBuffer sb2 = sb;
 	StringBuffer sb3 = new StringBuffer("Chester");
 	sb=sb3;
 	sb3=null;
 	sb2=null;
     }
 }

Choose the one below:

  1. Line 11
  2. Line 9
  3. Line 12
  4. Line 13

15 . What will be the output?

public class HarHam{
	public static void main(String argv[]){
		HarHam hh = new HarHam();
		hh.go();
        }
        public void go(){
	  String har = new String ("har");
	  String ham = new String("har");

	  collar:
	  for(int i=0; i  0){
		continue collar;
 	     }
	     System.out.print(i);
	  } // for i
	}
}

Choose the one below:

  1. Compile time error, System.out has no print method
  2. No output at runtime
  3. Output of 0
  4. Compile error, break cannot occur after its target label

16 . What will be the output?

protected class Wmid{
    private Wmid(String sName){
	System.out.println("Wmid");
    }

    Wmid(){}
}

public class Ombers extends Wmid{
    public static void main(String argv[]){
	Ombers o = new Ombers();
    }

}

Choose the one below:

  1. Compile time error, class Wmid may not be marked as protected
  2. Compile time error, a constructor may not be marked as private
  3. Compilation and output of Wmid
  4. Compilation but no output

17 . What will be the output?

public class Mickle  extends Thread implements Runnable{
    public static void main(String argv[]){
	Mickle m = new Mickle();
	m.start();

    }
    public void run(){
	go();
    }
     public void  go(){
	int i;
	while(true){
	    try{
		wait();
		System.out.println("interrupted");
	    }catch (InterruptedException e) {}
	}
    }
}

Choose the one below:

  1. Compile time error
  2. Compilation but runtime exception
  3. Compilation but no output at runtime
  4. Compilation and output of “interrupted” at runtime

18 . Which of the following statements are true?

  1. A LinkedHashMap preserves the order in which objects are added
  2. A TreeMap ensures that its elements will be in sorted order
  3. Elements in a LinkedList are sorted but not ordered
  4. Collections that implement the List interface allow duplicate elements

19 . What will be the output?

public class TechnoSample {
	public static void main(String[] args) {
		int i=3;
		System.out.println(getBoolean()? i=2*i++:i+++ ++i);
	}

	public static boolean getBoolean(){
		if((int)(Math.random()*2)==0)
			return false;
		else
			return true;
	}
}

Choose the one below:

  1. Prints randomly 6 or 8 at each execution
  2. Prints randomly 7 or 8 at each execution
  3. Always prints 6 at each execution
  4. Prints randomly 6 or 11 at each execution
  5. Compilation error

20 . An ArithmeticException is a checked exception. True Or False?

  1. True
  2. False

21 . Assume the bit pattern of byte x is: 10110001. What will the sign of x be after x >> 2?

Choose the one below:

  1. Positive
  2. Negative

22 . In a switch statement, the argment to the case label (case argument:) can be any variable which can fit within an int. True/False?

  1. True
  2. False

23 . Overloaded methods must not throw new checked exceptions not thrown by the original method. True/False?

  1. True
  2. False

24 . Which of the following statements are true?

  1. Assigning null to a reference causes the object to be garbage collected
  2. Assigning null to a reference causes the object to become eligable for garbage collection
  3. An object is eligable for garbage collection once it is unreachable via any reference
  4. Any object created within a method will be eligable for garbage collection once the method ceases execution

25 . Which of the following statements are true about the LinkedHashSet class?

  1. It may not contain duplicate elements
  2. The elements are ordered but not sorted
  3. The elements are sorted
  4. It does not permit null elements

26 . Given the following code, which option if inserted after the line with the comment //Here will result in code that will compile and output SupEx?

class Super{
    public void go(){
	System.out.print("Super");
    }

}

public class SupEx extends Super{
    public static void main(String argv[]){
	//Here
	s.go();
    }
    public void go(){
	System.out.println("SupEx");
    }
}

Choose the one below:

  1. SupEx s = new Super();
  2. Super s = new SupEx();
  3. SupEx s = new SupEx();
  4. Super s = new Super();

27 . Which of the following will result in an output of 10?

  1. System.out.println(Math.round(10.1));
  2. System.out.println(Math.floor(10.1));
  3. System.out.println(Math.abs(10.1));
  4. System.out.println(Math.min(10.1));

28 . What will be the output?

public class Photos {
    private int iKey;
    private String sValue;

    public Photos(int iKey, String sValue){
        this.iKey=iKey;
	this.sValue=sValue;
    }

    public int hashCode(){
	return super.hashCode();
    }

    public boolean equals(Object o){
	if(o instanceof Photos){
	    if(this.hashCode() == o.hashCode()){
		return true;
	    }
	}
	return false;
    }
}

Choose the one below:

  1. The hashCode method is correctly implemented
  2. The hashCode method is not correct because it is inconsistant with the equals method
  3. The code will not compile because there is a circular reference to the hashCode method
  4. The code will not compile because the return value of this.hashCode is not an int value
  5. The code will not compile because it does not implement the comparable interface

29 . Which of the following statements are true?

  1. A higher priority Thread will prevent a lower priorty Thread from getting any access to the CPU
  2. The yield method only allows any higher priority priority thread to execute
  3. The Thread class has a static method called yield
  4. Calling yield with an integer parameter causes it to yield for a specific time

30 . How do you set the priority of the thread “newThread” to the minimum of two values: maximum priority and current priority incremented to the next level? [Use the Thread priority constants and do not insert any extra characters or leave any blank spaces]

31 . Variables declared within methods cannot be marked as static. True/False?

  1. True
  2. False

32 . What is the initial capacity of an empty StringBuffer object?

new StringBuffer()

(Note: No extra characters Or spaces)

33 . What is the capacity of strBuf object after executing the following statement?

    StringBuffer strBuf = new StringBuffer("Technopark");

Choose the one below:

  1. 0
  2. 6
  3. 25
  4. 255
  5. -1
  6. None of the above

34 . How can you remove the superfluous capacity of a StringBuffer object say strBuf (if there is any)?
(Hint: Use SetLength() and length() methods. Please do not include any extra characters Or spaces)

35 . What will be the output?

public class MyClass
{
    public static void main(String[] args)
    {
        String s = "hello";
        StringBuffer sb = new StringBuffer(s);

        sb.reverse();

        if (s == sb)
            System.out.println("a");
        if (s.equals(sb))
            System.out.println("b");
        if (sb.equals(s))
            System.out.println("c");
    }
} // MyClass

Choose the one below:

  1. The code will fail to compile, since the constructor of the String class is not properly called
  2. The code will fail to compile, since (s == sb) is an illegal expression
  3. The code will fail to compile, since the expression (s.equals(sb)) is illegal
  4. The code will print c when run
  5. The program will throw a ClassCastException when run

36 . At which point will the word “Harpic” be printed out when this code is executied?

class Harpic{
    public void finalize(){
	System.out.println("Harpic");
    }

}

public class ArmitageShanks{
    Harpic har;
    public static void main(String argv[]){
	ArmitageShanks as = new ArmitageShanks();
	as.oui();
    }
    public void oui(){
	har = new Harpic();
	mno(har);
	//one
	har=null;

    }
    public void mno(Harpic har){
	Harpic pic=har;
	//two
	pic=null;
	//three
	har=null;
    }
}

Choose the one below:

  1. After executing the line after the comment //one
  2. After executing the line after the comment //two
  3. After executing the line after the comment //three
  4. It is impossible to say, the String “Harpic” may not be output at all

37 . What will be the output?

class TSamp extends Thread {
    public native String getTime();
}

public class Multi implements Runnable {
    boolean bStop;
    public static void main(String argv[]){
	Multi m = new Multi();
	m.go();
    }
    public void go(){
	TSamp ts = new TSamp(this);
	ts.start();
	bStop=true;

    }
    public void run(){
	if(bStop==true){
	    return;
	}
	System.out.println("running");
    }
}

Choose the one below:

  1. Compilation, but output at runtime will cannot be exactly determined
  2. Compilation and output of “running”
  3. Compilation but no output at runtime
  4. Compile time error

38 . What will be the output?

public class Cote{
    public static void main(String argv[]){
        Cote c = new Cote();
        c.go(argv[0]);
    }
    public void go(String s){
        int i = Integer.parseInt(s);
        if(i > 0){
            System.out.println(i);
        }else{
            throw new AssertionError(i);
        }
    }
}

Choose the one below:

  1. Compile time error, AssertionError has no int constructor
  2. Compile time error AssertionError does not exist
  3. Assertion Error at runtime if given a command line parameter of 0
  4. If given a command line parameter of 1, 1 will be output at runtime

39 . What will be the output?

import java.util.*;
public class Chawson{
	public static void main(String argv[]){
	Chawson c = new Chawson();
	c.whittan();
}
public void whittan(){
	HashSet hs = new HashSet();
	hs.add("one");
	hs.add("two");
	hs.add("one");
	wyche(hs);
}
	public void wyche(Set s){
		HashSet hs = (HashSet) s;
		System.out.println(hs.size());
	}
}

Choose the one below:

  1. Compilation and output of 3
  2. Compile time error, duplicate elements cannot be added to HashSet
  3. Runtime error due to an attempt to add duplicate elements to a HashSet
  4. Compilation and output of 2

40 . AssertionError exceptions are checked exceptions. True Or False?

  1. True
  2. False

41 . What will be the output?

 public static void main(String[] args ){
   int n = 11 ;
   do {
     System.out.print( " " + n-- );
   }while( (n % 4) != 0 );
   System.out.println( " final " + n );
 }

Choose the one below:

  1. 11 10 9 final 8
  2. 10 9 8 final 8
  3. 11 10 9 8 final 8
  4. 11 final 10

42 . Consider the following main method in the TechnoSample class:

 public static void main (String[] args){
   String s1 = " Arg " + args[1] ;
   s1.trim();
   String s2 = ":" + s1 + args[2] ;
   System.out.println( s2 + ":" );
 }

What will be printed when this is executed with the following command line?

java TechnoSample alpha beta gamma delta

Choose the one below:

  1. :Arg betagamma:
  2. :Argbetagamma:
  3. :Arg betagamma:
  4. :Arg alphabeta:
  5. :Arg alphabeta:

43 . What will be the output?

class WornPadException extends RuntimeException{
}
public class Wheel{
public static void main(String argv[]){
Wheel w = new Wheel();
System.out.print(w.roll());
}
public int roll(){
int iDistance =0;
try{
for(int i =0; i < 2 ;i ++){
System.out.print("roll");
iDistance = iDistance * i;
}
return iDistance;
}finally{
brake();
System.out.print("finished");
return iDistance+1;
}
}
public void brake() throws WornPadException{
System.out.print("brake");
}
}

Choose the one below:

  1. Compile time error, calls to brake must be within a try/catch block
  2. Compile time error the try block has no catch clause
  3. Runtime error, the call to brake is not within a try/catch block
  4. Runtime error the call to brake is within a finally clause
  5. Compilation and output of rollrollbrakefinished0
  6. Compilation and output of rollrollbrakefinished1

44 . Select all of the following statements that are true?

  1. The Float class has constructors that take type String, type double and type float
  2. The * operator can be used to multiply the values of instances of the Integer class
  3. The setValue method can be used to alter the value of an instance of Integer, Float or Double
  4. The Character class can store either a char value or a String value
  5. The Integer.parseInt method will convert an appropriate String to its int value

45 . When programming a local inner class inside a method code block, which of the following statements is true?

  1. The inner class will only have access to static variables in the enclosing class
  2. The inner class can use any local variables declared in the method
  3. The only local variables an inner class can use are those that are declared final
  4. The only local variables an inner class can use are those that are declared static
  5. The inner class will only have access to instance and local variables if they are declared final

46 . Which of the following are public variables or methods that belong to an instance of Thread?
Do not select static variables, static methods, or deprecated methods?

  1. wait() method
  2. sleep() method
  3. start() method
  4. MAX_PRIORITY – an int variable
  5. daemon – a boolean variable

47 . Which of the following is not a Java keyword? (Java SDK v1.4)

  1. transient
  2. generic
  3. assert
  4. strictfp
  5. friend
  6. sizeof

48 . What will be the output?

public class TechnoSample{

 static Object theObj ;
 static Object[] someObj ;
 static String letters[] = {"A", "B", "C", "D" };
 static char[] caps = {'A', 'B', 'C', 'D' };

 public static void main (String[] args){
   someObj = new Object[ 3 ] ;
   int[] theInts = null ;
   // what can go here?
 }

Choose the one below:

  1. theInts = caps;
  2. theObj = theInts;
  3. someObj = theInts;
  4. theObj = caps;

49 . What will be the output?

 public void testC(char ch) {
   Integer ss = new Integer( ch );
   Character cc = new Character( ch ) ;
   if( ss.equals( cc )) System.out.println("equals");
   if( ss.intValue() == cc.charValue() ){
       System.out.println("EQ");
   }
 }

Choose the one below:

  1. The compiler will object to line 4 because the object types of ss and cc don’t match
  2. The program will compile and run, producing “EQ”
  3. The program will compile and run, producing “equalsEQ”
  4. The program will compile and run, producing “equals”
  5. The compiler will object to creating an Integer from a char in line 2

50 . Your program has two object references, x and y. In some method the following logical tests are done:

    boolean hashFlag = ( x.hashCode() == y.hashCode() );
    boolean equalsFlag = x.equals( y );
    boolean eqFlag = ( x == y );

Which of the following statements about the relationship between these tests are true?

  1. If equalsFlag is true, then hashFlag must be true
  2. If hashFlag is true, then eqFlag must be true
  3. If equalsFlag is false, then eqFlag must be false
  4. if hashFlag is false, then eqFlag must be false

Answers

1 : 2 & 3 is correct. 
Explanation:
pause() and halt() are not methods of the Thread class.

2 : 2 is correct. 
Explanation:
Please see the Java 1.4 documentation.

3 : 2 is correct. 
Explanation:
Although bContinue does get set to true, the setPrice call is blocked because setPrice and run are both synchronized.

4 : 4 is correct. 
Explanation:
If that seems a vauge answer it is because you cannot be certain of the system that the underlying OS uses for allocating cycles for a Thread. The chances are that once the thread has been spun off in the call to start in the methodname() the main method will run to completion and the value of sName will still be vandeluer before the Thread modifies it. You cannot be certain of this though.

Just because sName is static does not mean that passing it to a method gives the method the original copy. The method only sees a locally created copy and any changes to it will not be reflected on return to the calling method.

5 : 2 & 3 is correct. 
Explanation:
Generally speaking, all I/O operations require explicit exception handling with try/catch blocks. The JDK 1.4 exams does not explicitly cover I/O but it may be referred to in the context of exception handling.

6 : 1 is correct. 
Explanation:
This is a bit of a sneaky one as the Math.random method returns a pseudo random number between 0 and 1, and thus option 3 is a plausible Answer. However the number returned is a double and so the compiler will complain that a cast isneeded to convert a double to an int.

7 : 4 is correct. 
Explanation:
All wrapper class objects are immutable.

8 : 2 is correct. 
Explanation:
The TreeMap class stores the keys rather than the values in sorted order.

9 : 3 is correct. 
Explanation:
Constructors are executed in order of the oldest ancester down, so the output from Biddy is seen before Val. Although the the paremeter for shep has no floating point component, a widening conversion involves no loss of precisionand thus the value is cast to a float by the method shep. By default a float will have a decimal component and thus it has a trailing zero in this example.

10 : 2,3 & 4 is correct. 
Explanation:
Please see Java 1.2/1.4 API documentation.

11 : 1 is correct. 
Explanation:
An int cannot have a fractional component, under JDK1.4 this produced the error message

possible loss of precision found : double required: int
private int iAcres=3.5;

12 : 2 & 3 is correct. 
Explanation:
A variable declared as public within a method is only visible within the method. They are sometimes called automatic variables as they automatically come into scope when the method runs and are out of scope when the method hasfinished execution. Variables declared within methods cannot be marked as static. A method declared with no visibility modifier is accessible anywhere from within the current package.A method declared with the protected modifier is also accessible in child classes that are not in the current package.

13 : 3 is correct. 
Explanation:
Option 4 is incorrect because an assert statment must make a comparison and the single = sign indicates an assignment.The assert statement does not use curly braces and assert cannot be used like a parameterless method call as in assert() in option 1.

14 : 4 is correct. 
Explanation:
On line 9 the object created on line 8 has the reference sb2 pointed to it. Until something happens to make that reference unable to reach the object it will not be eligible for garbage collection.

15 : 3 is correct. 
Explanation:
The == operator should never be used to test the equivalence of strings as it will only test the reference, not the sequence of characters. To test if the Strings match use the String equals() method.

16 : 1 is correct. 
Explanation:
There is no rule against constructors being marked as private.

17 : 2 is correct. 
Explanation:
This code will produce a java.lang.IllegalMonitorStateException at runtime because the wait/notify code is not within synchronized code.

18 : 1,2 & 4 is correct. 
Explanation:
The LinkedHashMap was added with JDK1.4. Option 3 is nonsense because if something is sorted that imposes an order (however something may be ordered without being sorted).

19 : 1 is correct. 
Explanation:
No problem here, the code compiles fine. One thing to be aware of is that i+++ ++i compiles fine because of the way Java code is actually parsed. The parser tokenizes the source in bunches of longest valid character sequences. i+++ ++i will betokenized as i,++,+,++,i and interpreted as i++ + ++i, that is i post-incremented plus i pre-incremented. Then you have to know how the ternary conditional ?: operator works, that is, it always evaluates its first operand and then depending onthe results, evaluates the second OR the third operand (never both). So getBoolean() returns either true or false, thus the code either prints i=2*i++ or i+++ ++i. The former is equivalent to i=2*i and the latter to 2*i+2.

20 : 2 is correct. 
Explanation:
ArithmeticExceptions are considered programmer problems, and are not checked by the compiler. A divide-by-zero error, for example, should be checked for by your own code. (from Java Ranch round up game)

21 : 2 is correct. 
Explanation:
The right shift operator fills all bits from the left with the same value as the original sign bit — in this case 1. (from Java Ranch round up game)

22 : 2 is correct. 
Explanation:
The case argument must be either an int literal, or an int-compatible variable which is a constant ie., static final.

23 : 2 is correct. 
Explanation:
This would be true for overriding methods, but overloaded methods are free to throw new checked exceptions. (from Java Ranch)

24 : 3 is correct. 
Explanation:
Assigning null to a reference will only cause the object it references to be ready for garbage collection if no other reference points to it.It is possible to create an object inside a method and to also assign a reference created outside the method to the same object,so the completion of a method is no guarantee that an object is eligable for garbage collection.

25 : 1 & 2 is correct. 
Explanation:
Please see the relevant API.

26 : 2 & 3 is correct.

27 : 1 is correct. 
Explanation:
Options 2 will output 10.0 and option 3 will output 10.1. Option 4 will cause a compilation error, because the Math.min method takes two arguments (from www.examulator.com)

28 : 1 is correct. 
Explanation:
This represents a fairly useless but correct implementation of hashCode by using the version inherited from Object which uses the memory address of the object to generatethe hashCode value. (from www.examulator.com)

29 : 3 is correct. 
Explanation:
A call to yield can allow any waiting thread to execute depending on the scheduling system of the underlying operating system. There is no version of yield that takes aninteger parameter.Weather a higher priority thread gets CPU time than a lower priorty thread is platform dependent and cannot be certain. (from www.examulator.com)

30 : newThread.setPriority(Math.min(Thread.MAX_PRIORITY,newThread.getPriority()+1));

31 : 1 is correct.

32 : 16.
Explanation:
The default capacity for any StringBuffer object is 16 + the length of the String specified as the argument. If none specified, it will be 16. Capacity can also be specifiedusing the other constructor StringBuffer(int capacity).

33 : 3 is correct. 
Explanation:
Capacity of a StringBuffer object is always the length of the string + 16 (unless the capacity is specified using StringBuffer(int capacity))

34 : strBuf.setLength(strBuf.length());
Explanation:
Please see the StringBuffer API.

35 : 2 is correct. 
Explanation:
The expression tries to compare two references and will fail, since neither String nor StringBuffer is a super class of the other [from Khalid's book]

36 : 4 is correct. 
Explanation:
The instance of the Harpic class will probably not be garbage collected at all, and thus the finalize method will not be run (but it could be).(from www.examulator.com)

37 : 4 is correct. 
Explanation:
The TSamp has no constructor defined that takes a class of type Runnable, and as constructors are not inherited the code will not compile. (from www.examulator.com)

38 : 3 & 4 is correct.

39 : 4 is correct. 
Explanation:
Because the code attempts to insert the string “one” twice, the HashSet hs has only two elements.
It is a good idea when using the add method of HashSet to check the boolean value returned to ensure that the new element wassuccessfully added.

40 : 2 is correct. 
Explanation:
java.lang.AssertionError class is a subclass of java.lang.Error and that makes it unchecked.

41 : 1 is correct. 
Explanation:
Note that n is decremented after the value is printed. (from LanWrights exam)

42 : 3 is correct. 
Explanation:
The result is “: Arg betagamma:” because the call to trim() does not change s1. (from LanWrights exam)

43 : 6 is correct. 
Explanation:
Choice 1 & 2 are not correct, ’cause WornPadException extends RuntimeException it is not mandatory to surround calls to it with a try/catch block. Choice 3 is not correct since thecompiler checks the need for try/catch, not the runtime. Choice 4 is not correct, because a finally clause can have any code in it. Choice 5 is not correct, since the final valuereturned is 1. Choice 6 is correct because WornPadException extends RuntimeException it is not mandatory to surround calls to it with a try/catch block. It is perfectly correct &sometimes useful to have a try/finally block without a catch statement. Because the finally clause ‘ll be executed the value returned ‘ll be that within the finally clause.

44 : 1 & 5 is correct. 
Explanation:
The * operator can only work with primitives. The value in a wrapper class object can’t be changed once created. The Character class can only store a char value.(from LanWrights exam)

45 : 3 is correct. 
Explanation:
Only local variables declared final can be used by the inner class. (from LanWrights exam)

46 : 1 & 3 is correct. 
Explanation:
Since wait is a method in Object and Thread is an object; sleep is a static method; start is an instance method of Thread; MAX_PRIORITY is a static final variable of Thread;the daemon boolean variable is a private instance variable. (from LanWrights exam)

47 : 2,5 & 6 is correct. 
Explanation:
transient is used as a modifier for variables; generic is not a keyword; as of Java 1.4, assert is a keyword; the keyword strictfp controls floating point calculations; friend is nota keyword; Java does not use sizeof.

48 : 2 & 4 is correct. 
Explanation:
you can’t cast any primitive array to another primitive array type, no matter how reasonable it seems; any array can be cast to an Object reference; you can’t cast a primitive arrayto an reference type array. The compiler does not care that theInts will have a null value when the program runs. (from LanWrights exam)

49 : 2 is correct. 
Explanation:
the equals method is defined in terms of taking an Object reference so there is no problem; the equals test fails because the objects are of different types, but the charValuereturn is promoted to int and the result is true; the equals test fails because the objects are of different types; only the == comparison will result in true. Note that the compilerpromotes the charValue return to int; promotion of the char value to int is automatic. (Credit: LanWrights)

50 : 1,3 & 4 is correct. 
Explanation:
(1) yes, this is a requirement for hashcodes and the equals method; (2) no, two objects not equal by the == test may still have identical hashcodes (3) Yes, if the equals() testreturns false, x and y can’t possibly refer to the same object (4) Yes, this is a requirement for hashcodes and the equals method. (Credit: LanWrights)

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About Krishna Srinivasan

He is Founder and Chief Editor of JavaBeat. He has more than 8+ years of experience on developing Web applications. He writes about Spring, DOJO, JSF, Hibernate and many other emerging technologies in this blog.

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