Object class - Java test

Object class - Java test


1) In object class parent class reference variable can refer the child class object, known as?

A) Upcasting
B) Implicit casting
C) Explicit casting
D) Boolean casting
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ANSWER: A) Upcasting




2) Which method compares the given object to this object?

A) public boolean equals(Object obj)
B) public final void notifyAll()
C) public final void notify()
D) public final ClassgetClass()
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ANSWER: A) public boolean equals(Object obj)




3) Which method causes the current thread to wait for the specified milliseconds, until another thread notifies? (invokes notify() or notifyAll() method)?

A) public final void wait(long timeout)throws InterruptedException
B) protected void finalize()throws Throwable
C) public final void wait(long timeout,int nanos)throws InterruptedException
D) protected Object clone() throws CloneNotSupportedException
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ANSWER: A) public final void wait(long timeout)throws InterruptedException




4) The object cloning is a way to create exact copy of an object?

A) True
B) False
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ANSWER: A) True




5) The clone() method is defined in?

A) Abstract class
B) Object Class
C) ArrayList class
D) None of the above
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ANSWER: B) Object Class




6) Which method of object class can clone an object?

A) copy()
B) Objectcopy()
C) Objectclone()
D) Clone()
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ANSWER: C) Objectclone()




7) Which is an acronym for, it physically exists; it contains JRE + development tools?

A) JRE
B) JVM
C) JDK
D) None of the above
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ANSWER: C) JDK




8) The JDK forms an extended subset of a software development kit (SDK)?

A) True
B) False
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ANSWER: A) True




9) In which the standard collection classes implements a linked list data structure?

A) LinkedList
B) AbstractList
C) HashSet
D) Both B & C

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ANSWER: A) LinkedList




10) Which extends the AbstractList class and implements List and Deque interfaces?

A) AbstractList
B) LinkedList
C) HashSet
D) None of the above
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ANSWER: B) LinkedList




11) Generally string is a sequence of characters, But in java, string is an

A) Object
B) Class
C) Package
D) None of the above
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ANSWER: A) Object




12) In which string class function returns the number of characters in a string?

A) length()
B) replace()
C) charAt()
D) equalIgnoreCase()
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ANSWER: A) length()




13) String class in encapsulated under which package?

A) java.lang
B) java.util
C) java.io
D) java.awt
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ANSWER: A) java.lang




14) Java defines a peer class of String, called?

A) StringBuffer
B) StringBuilder
C) Both A & B
D) None of the above
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ANSWER: A) StringBuffer




15) Which concept is used to make Java more memory efficient (because no new objects are created if it exists already in string constant pool)?

A) String literal
B) By new keyword
C) Both A & B
D) None of the above
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ANSWER: A) String literal




16) Which method of string class in java Returns a new string that is a substring of this string?

A) public String substring(int beginIndex,int endIndex)
B) public String substring(int beginIndex)
C) public boolean equalsIgnoreCase(String another)
D) Both A & B
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ANSWER: D) Both A & B




17) Which method of string class in java is used to converts the boolean into String?

A) public static String valueOf(double i)
B) public static String valueOf(boolean i)
C) public boolean equals(Object anObject)
D) public static String valueOf(Object obj)
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ANSWER: B) public static String valueOf(boolean i)




18) A pool of strings, initially empty, is maintained privately by the class String?

A) intern() method
B) length() method
C) trim() method
D) charAt() method
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ANSWER: A) intern() method




19) The following program is an example of?

class Simple{
public static void main(String args[]){

String s="Sachin";
System.out.println(s.length());//6
}
}

A) length() method
B) intern() method
C) trim() method
D) charAt() method
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ANSWER: A) length() method




20) Which class is thread-safe i.e. multiple threads cannot access it simultaneously,So it is safe and will result in an order?

A) StringBuffer class
B) StringBuilder class
C) Both A & B
D) None of the above
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ANSWER: A) StringBuffer class




21) Which constructor creates an empty string buffer with the specified capacity as length.

A) StringBuffer()
B) StringBuffer(String str)
C) StringBuffer(int capacity)
D) None of the above
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ANSWER: C) StringBuffer(int capacity)




22) This method of StringBuffer Class is used to insert the specified string with this string at the specified position?

A) public synchronized StringBuffer append(String s)
B) public synchronized StringBuffer insert(int offset, String s)
C) public String substring(int beginIndex)
D) public int length()
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ANSWER: B) public synchronized StringBuffer insert(int offset, String s)




23) By overriding the toString() method of the Object class, we can return values of the object, so we don't need to write much code?

A) True
B) False
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ANSWER: A) True




24) How many constructors are defined in StringTokenizer class?

A) 2
B) 3
C) 4
D) 5
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ANSWER: B) 3




25) The Object class is not a parent class of all the classes in java by default?

A) True
B) False
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ANSWER: B) False



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    Discussion

  • RE: Object class - Java test -JavaCrazy (10/09/15)
  • A few more questions have wrong answers.
  • RE: Object class - Java test -JavaGuru (10/09/15)
  • nice!!!
  • RE: Object class - Java test -Anupriya (10/09/15)
  • The answer to the question "Which method of object class can clone an object?" is wrong . The correct answer is "clone()" and not "√∂bjectCone()" . Please get it corrected .