Core Java 1

20 Questions | By JQuizMaster | Updated: Mar 15, 2016 | Attempts: 268

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This questions are about the core java concepts includeing language fundamentals, objects,interfaces,threads,loops,collections and garbage collections. . .

Questions and Answers

1.
Which three are valid declarations of a char?
1. char c1 = 064770;
2. char c2 = 'face';
3. char c3 = 0xbeef;
4. char c4 = \u0022;
5. char c5 = '\iface';
6. char c6 = '\uface';
- A.
  
  1,2,4
- B.
  
  1,3,6
- C.
  
  3,5
- D.
  
  5 only
Correct Answer
B. 1,3,6
2.
Which four options describe the correct default values for array elements of the types indicated?
1. int -> 0
2. String -> "null"
3. Dog -> null
4. char -> '\u0000'
5. float -> 0.0f
6. boolean -> true
- A.
  
  1,2,3,4
- B.
  
  1,3,4,5
- C.
  
  2,4,5,6
- D.
  
  3,4,5,6
Correct Answer
B. 1,3,4,5
3.

Public class Outer { public void someOuterMethod() { //Line 5 } public class Inner { } public static void main(String[] argv) { Outer ot = new Outer(); //Line 10 } } Which of the following code fragments inserted, will allow to compile?
- A.
  
  New Inner(); //At line 5
- B.
  
  New Inner(); //At line 10
- C.
  
  New ot.Inner(); //At line 10
- D.
  
  New Outer.Inner(); //At line 10
Correct Answer
A. New Inner(); //At line 5
4.

Which cause a compiler error? (choose all that apply)
- A.
  
  Float[ ] f = new float(3);
- B.
  
  Float f2[ ] = new float[ ];
- C.
  
  Float[ ]f1 = new float[3];
- D.
  
  Float f3[ ] = new float[3];
Correct Answer(s)
A. Float[ ] f = new float(3);
B. Float f2[ ] = new float[ ];
5.

Public class Runner { public static void main(String args[]) { System.out.println(“This is a correct program”); continue; } } State True or False: The above program prints a output
- A.
  
  True
- B.
  
  False
Correct Answer
B. False
6.

What will be the output of the program? class Test { public static void main(String [] args) { int x=20; String sup = (x < 15) ? "small" : (x < 22)? "tiny" : "huge"; System.out.println(sup); } }
- A.
  
  Small
- B.
  
  Tiny
- C.
  
  Huge
- D.
  
  Compilation fails
Correct Answer
B. Tiny
7.

What will be the output of the program? class Bitwise { public static void main(String [] args) { int x = 11 & 9; int y = x ^ 3; System.out.println( y | 12 ); } }
- A.
  
  0
- B.
  
  7
- C.
  
  8
- D.
  
  14
Correct Answer
D. 14
8.

What will be the output of the program? public class X { public static void main(String [] args) { try { badMethod(); System.out.print("A"); } catch (Exception ex) { System.out.print("B"); } finally { System.out.print("C"); } System.out.print("D"); } public static void badMethod() {} }
- A.
  
  AC
- B.
  
  BC
- C.
  
  ACD
- D.
  
  ABCD
Correct Answer
C. ACD
9.

Public void test(int x) { int odd = 1; if(odd) /* Line 4 */ { System.out.println("odd"); } else { System.out.println("even"); } } Which statement is true?
- A.
  
  Compilation fails
- B.
  
  "odd" will always be output.
- C.
  
  "even" will always be output.
- D.
  
  "odd" will be output for odd values of x, and "even" for even values.
Correct Answer
A. Compilation fails
10.

try { int x = 0; int y = 5 / x; } catch (Exception e) { System.out.println("Exception"); } catch (ArithmeticException ae) { System.out.println(" Arithmetic Exception"); } System.out.println("finished"); State True or False: The output of the above code is the below Exception finished
- A.
  
  True
- B.
  
  False
Correct Answer
B. False
11.

Suppose that you would like to create an instance of a new Map that has an iteration order that is the same as the iteration order of an existing instance of a Map. Which concrete implementation of the Map interface should be used for the new instance?
- A.
  
  TreeMap
- B.
  
  HashMap
- C.
  
  LinkedHashMap
- D.
  
  The answer depends on the implementation of the existing instance.
Correct Answer
C. LinkedHashMap
12.

Which collection class allows you to associate its elements with key values, and allows you to retrieve objects in FIFO (first-in, first-out) sequence?
- A.
  
  Java.util.ArrayList
- B.
  
  Java.util.LinkedHashMap
- C.
  
  Java.util.HashMap
- D.
  
  Java.util.TreeMap
Correct Answer
B. Java.util.LinkedHashMap
13.

/* Missing Statement ? */ public class foo { public static void main(String[]args)throws Exception { java.io.PrintWriter out = new java.io.PrintWriter(); new java.io.OutputStreamWriter(System.out,true); out.println("Hello"); } } What line of code should replace the missing statement to make this program compile?
- A.
  
  No statement required.
- B.
  
  Import java.io.*;
- C.
  
  Import java.io.PrintWriter;
- D.
  
  #include java.io.*;
Correct Answer
A. No statement required.
14.

Which of the following are Java reserved words?
- A.
  
  Constant
- B.
  
  Null
- C.
  
  Default
- D.
  
  Implement
Correct Answer(s)
B. Null
C. Default
15.

State the below statement is not false about static nested class: It’s variables and methods must be static
- A.
  
  True
- B.
  
  False
Correct Answer
B. False
16.

Class X implements Runnable { public static void main(String args[]) { /* Missing code? */ } public void run() {} } Which of the following line of code is suitable to start a thread ?
- A.
  
  Thread t = new Thread(X);
- B.
  
  Thread t = new Thread(X); t.start();
- C.
  
  X run = new X(); Thread t = new Thread(run); t.start();
- D.
  
  Thread t = new Thread(); x.run();
Correct Answer
C. X run = new X(); Thread t = new Thread(run); t.start();
17.
Which three guarantee that a thread will leave the running state?
1. yield()
2. wait()
3. notify()
4. notifyAll()
5. sleep(1000)
6. aLiveThread.join()
7. Thread.killThread()
- A.
  
  1,2 and 4
- B.
  
  2,5 and 6
- C.
  
  3,4 and 7
- D.
  
  4,5 and 7
Correct Answer
B. 2,5 and 6
18.

Public class X { public static void main(String [] args) { X x = new X(); X x2 = m1(x); /* Line 6 */ X x4 = new X(); x2 = x4; /* Line 8 */ doComplexStuff(); } static X m1(X mx) { mx = new X(); return mx; } } After line 8 runs. how many objects are eligible for garbage collection?
- A.
  
  0
- B.
  
  1
- C.
  
  2
- D.
  
  3
Correct Answer
B. 1
19.

Which of the following would compile without error?
- A.
  
  Int a = Math.abs(-5);
- B.
  
  Int b = Math.abs(5.0);
- C.
  
  Int c = Math.abs(5.5F);
- D.
  
  Int d = Math.abs(5L);
Correct Answer
A. Int a = Math.abs(-5);
20.

What is the output for the below code ? public class A { public A() { System.out.println("A"); } } public class B extends A implements Serializable { public B() { System.out.println("B"); } } public class Test { public static void main(String... args) throws Exception { B b = new B(); ObjectOutputStream save = new ObjectOutputStream(new FileOutputStream("datafile")); save.writeObject(b); save.flush(); ObjectInputStream restore = new ObjectInputStream(new FileInputStream("datafile")); B z = (B) restore.readObject(); } }
- A.
  
  A B A
- B.
  
  A B A B
- C.
  
  B B
- D.
  
  A B
Correct Answer
A. A B A

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Current Version
Mar 15, 2016

Quiz Edited by
ProProfs Editorial Team
Dec 15, 2011

Quiz Created by
JQuizMaster

Core Java 1

Which three are valid declarations of a char?

char c1 = 064770;

char c2 = 'face';

char c3 = 0xbeef;

char c4 = \u0022;

char c5 = '\iface';

char c6 = '\uface';

Which four options describe the correct default values for array elements of the types indicated?

int -> 0

String -> "null"

Dog -> null

char -> '\u0000'

float -> 0.0f

boolean -> true

Public class Outer { public void someOuterMethod() { //Line 5 } public class Inner { } public static void main(String[] argv) { Outer ot = new Outer(); //Line 10 } } Which of the following code fragments inserted, will allow to compile?

Which cause a compiler error? (choose all that apply)

Public class Runner { public static void main(String args[]) { System.out.println(“This is a correct program”); continue; } } State True or False: The above program prints a output

What will be the output of the program? class Test { public static void main(String [] args) { int x=20; String sup = (x < 15) ? "small" : (x < 22)? "tiny" : "huge"; System.out.println(sup); } }

What will be the output of the program? class Bitwise { public static void main(String [] args) { int x = 11 & 9; int y = x ^ 3; System.out.println( y | 12 ); } }

What will be the output of the program? public class X { public static void main(String [] args) { try { badMethod(); System.out.print("A"); } catch (Exception ex) { System.out.print("B"); } finally { System.out.print("C"); } System.out.print("D"); } public static void badMethod() {} }

Public void test(int x) { int odd = 1; if(odd) /* Line 4 */ { System.out.println("odd"); } else { System.out.println("even"); } } Which statement is true?

try { int x = 0; int y = 5 / x; } catch (Exception e) { System.out.println("Exception"); } catch (ArithmeticException ae) { System.out.println(" Arithmetic Exception"); } System.out.println("finished"); State True or False: The output of the above code is the below Exception finished

Suppose that you would like to create an instance of a new Map that has an iteration order that is the same as the iteration order of an existing instance of a Map. Which concrete implementation of the Map interface should be used for the new instance?

Which collection class allows you to associate its elements with key values, and allows you to retrieve objects in FIFO (first-in, first-out) sequence?

Which of the following are Java reserved words?

State the below statement is not false about static nested class: It’s variables and methods must be static

Class X implements Runnable { public static void main(String args[]) { /* Missing code? */ } public void run() {} } Which of the following line of code is suitable to start a thread ?

Which three guarantee that a thread will leave the running state?

yield()

wait()

notify()

notifyAll()

sleep(1000)

aLiveThread.join()

Thread.killThread()

Public class X { public static void main(String [] args) { X x = new X(); X x2 = m1(x); /* Line 6 / X x4 = new X(); x2 = x4; / Line 8 */ doComplexStuff(); } static X m1(X mx) { mx = new X(); return mx; } } After line 8 runs. how many objects are eligible for garbage collection?

Which of the following would compile without error?

Core Java 1

Which three are valid declarations of a char? char c1 = 064770; char c2 = 'face'; char c3 = 0xbeef; char c4 = \u0022; char c5 = '\iface'; char c6 = '\uface';

Which four options describe the correct default values for array elements of the types indicated? int -> 0 String -> "null" Dog -> null char -> '\u0000' float -> 0.0f boolean -> true

Public class Outer { public void someOuterMethod() { //Line 5 } public class Inner { } public static void main(String[] argv) { Outer ot = new Outer(); //Line 10 } } Which of the following code fragments inserted, will allow to compile?

Which cause a compiler error? (choose all that apply)

Public class Runner { public static void main(String args[]) { System.out.println(“This is a correct program”); continue; } } State True or False: The above program prints a output

What will be the output of the program? class Test { public static void main(String [] args) { int x=20; String sup = (x < 15) ? "small" : (x < 22)? "tiny" : "huge"; System.out.println(sup); } }

What will be the output of the program? class Bitwise { public static void main(String [] args) { int x = 11 & 9; int y = x ^ 3; System.out.println( y | 12 ); } }

What will be the output of the program? public class X { public static void main(String [] args) { try { badMethod(); System.out.print("A"); } catch (Exception ex) { System.out.print("B"); } finally { System.out.print("C"); } System.out.print("D"); } public static void badMethod() {} }

Public void test(int x) { int odd = 1; if(odd) /* Line 4 */ { System.out.println("odd"); } else { System.out.println("even"); } } Which statement is true?

try { int x = 0; int y = 5 / x; } catch (Exception e) { System.out.println("Exception"); } catch (ArithmeticException ae) { System.out.println(" Arithmetic Exception"); } System.out.println("finished"); State True or False: The output of the above code is the below Exception finished

Suppose that you would like to create an instance of a new Map that has an iteration order that is the same as the iteration order of an existing instance of a Map. Which concrete implementation of the Map interface should be used for the new instance?

Which collection class allows you to associate its elements with key values, and allows you to retrieve objects in FIFO (first-in, first-out) sequence?

Which of the following are Java reserved words?

State the below statement is not false about static nested class: It’s variables and methods must be static

Class X implements Runnable { public static void main(String args[]) { /* Missing code? */ } public void run() {} } Which of the following line of code is suitable to start a thread ?

Which three guarantee that a thread will leave the running state? yield() wait() notify() notifyAll() sleep(1000) aLiveThread.join() Thread.killThread()

Public class X { public static void main(String [] args) { X x = new X(); X x2 = m1(x); /* Line 6 */ X x4 = new X(); x2 = x4; /* Line 8 */ doComplexStuff(); } static X m1(X mx) { mx = new X(); return mx; } } After line 8 runs. how many objects are eligible for garbage collection?

Which of the following would compile without error?

Which three are valid declarations of a char?

char c1 = 064770;

char c2 = 'face';

char c3 = 0xbeef;

char c4 = \u0022;

char c5 = '\iface';

char c6 = '\uface';

Which four options describe the correct default values for array elements of the types indicated?

int -> 0

String -> "null"

Dog -> null

char -> '\u0000'

float -> 0.0f

boolean -> true

Which three guarantee that a thread will leave the running state?

yield()

wait()

notify()

notifyAll()

sleep(1000)

aLiveThread.join()

Thread.killThread()

Public class X { public static void main(String [] args) { X x = new X(); X x2 = m1(x); /* Line 6 / X x4 = new X(); x2 = x4; / Line 8 */ doComplexStuff(); } static X m1(X mx) { mx = new X(); return mx; } } After line 8 runs. how many objects are eligible for garbage collection?