Explore topic-wise MCQs in Engineering.

This section includes 219 Mcqs, each offering curated multiple-choice questions to sharpen your Engineering knowledge and support exam preparation. Choose a topic below to get started.

101.

What will be the output of the program? public class Test { private static float[] f = new float[2]; public static void main (String[] args) { System.out.println("f[0] = " + f[0]); } }

A. f[0] = 0
B. f[0] = 0.0
C. Compile Error
D. Runtime Exception
Answer» C. Compile Error
Discussion
102.

What will be the output of the program? import java.util.*; class H { public static void main (String[] args) { Object x = new Vector().elements(); System.out.print((x instanceof Enumeration)+","); System.out.print((x instanceof Iterator)+","); System.out.print(x instanceof ListIterator); } }

A. Prints: false,false,false
B. Prints: false,false,true
C. Prints: false,true,false
D. Prints: true,false,false
Answer» E.
Discussion
103.

What will be the output of the program? TreeSet map = new TreeSet(); map.add("one"); map.add("two"); map.add("three"); map.add("four"); map.add("one"); Iterator it = map.iterator(); while (it.hasNext() ) { System.out.print( it.next() + " " ); }

A. one two three four
B. four three two one
C. four one three two
D. one two three four one
Answer» D. one two three four one
Discussion
104.

What will be the output of the program? public static void main(String[] args) { Object obj = new Object() { public int hashCode() { return 42; } }; System.out.println(obj.hashCode()); }

A. 42
B. Runtime Exception
C. Compile Error at line 2
D. Compile Error at line 5
Answer» B. Runtime Exception
Discussion
105.

What will be the output of the program? int I = 0; label: if (I < 2) { System.out.print("I is " + I); I++; continue label; }

A. I is 0
B. I is 0 I is 1
C. Compilation fails.
D. None of the above
Answer» D. None of the above
Discussion
106.

What will be the output of the program? int i = l, j = -1; switch (i) { case 0, 1: j = 1; /* Line 4 */ case 2: j = 2; default: j = 0; } System.out.println("j = " + j);

A. j = -1
B. j = 0
C. j = 1
D. Compilation fails.
Answer» E.
Discussion
107.

What will be the output of the program? public class SwitchTest { public static void main(String[] args) { System.out.println("value =" + switchIt(4)); } public static int switchIt(int x) { int j = 1; switch (x) { case l: j++; case 2: j++; case 3: j++; case 4: j++; case 5: j++; default: j++; } return j + x; } }

A. value = 2
B. value = 4
C. value = 6
D. value = 8
Answer» E.
Discussion
108.

What will be the output of the program? public class If2 { static boolean b1, b2; public static void main(String [] args) { int x = 0; if ( !b1 ) /* Line 7 */ { if ( !b2 ) /* Line 9 */ { b1 = true; x++; if ( 5 > 6 ) { x++; } if ( !b1 ) x = x + 10; else if ( b2 = true ) /* Line 19 */ x = x + 100; else if ( b1 | b2 ) /* Line 21 */ x = x + 1000; } } System.out.println(x); } }

A. 0
B. 1
C. 101
D. 111
Answer» D. 111
Discussion
109.

What will be the output of the program? public class Test { private static int[] x; public static void main(String[] args) { System.out.println(x[0]); } }

A. 0
B. null
C. Compile Error
D. <i class="java-code">NullPointerException</i>
E. at runtime
Answer» E. at runtime
Discussion
110.

What will be the output of the program? import java.util.*; class I { public static void main (String[] args) { Object i = new ArrayList().iterator(); System.out.print((i instanceof List)+","); System.out.print((i instanceof Iterator)+","); System.out.print(i instanceof ListIterator); } }

A. Prints: false, false, false
B. Prints: false, false, true
C. Prints: false, true, false
D. Prints: false, true, true
Answer» D. Prints: false, true, true
Discussion
111.

What will be the output of the program? package foo; import java.util.Vector; /* Line 2 */ private class MyVector extends Vector { int i = 1; /* Line 5 */ public MyVector() { i = 2; } } public class MyNewVector extends MyVector { public MyNewVector () { i = 4; /* Line 15 */ } public static void main (String args []) { MyVector v = new MyNewVector(); /* Line 19 */ } }

A. Compilation will succeed.
B. Compilation will fail at line 3.
C. Compilation will fail at line 5.
D. Compilation will fail at line 15.
Answer» C. Compilation will fail at line 5.
Discussion
112.

What will be the output of the program? public class Test { public static void main (String[] args) { String foo = args[1]; String bar = args[2]; String baz = args[3]; System.out.println("baz = " + baz); /* Line 8 */ } } And the command line invocation: &gt; java Test red green blue

A. baz =
B. baz = null
C. baz = blue
D. Runtime Exception
Answer» E.
Discussion
113.

What will be the output of the program? public class Test { public static void main (String args[]) { String str = NULL; System.out.println(str); } }

A. NULL
B. Compile Error
C. Code runs but no output
D. Runtime Exception
Answer» C. Code runs but no output
Discussion
114.

What will be the output of the program? public class Switch2 { final static short x = 2; public static int y = 0; public static void main(String [] args) { for (int z=0; z &lt; 3; z++) { switch (z) { case x: System.out.print("0 "); case x-1: System.out.print("1 "); case x-2: System.out.print("2 "); } } } }

A. 0 1 2
B. 0 1 2 1 2 2
C. 2 1 0 1 0 0
D. 2 1 2 0 1 2
Answer» E.
Discussion
115.

What will be the output of the program? int i = 1, j = 10; do { if(i &gt; j) { break; } j--; } while (++i &lt; 5); System.out.println("i = " + i + " and j = " + j);

A. i = 6 and j = 5
B. i = 5 and j = 5
C. i = 6 and j = 4
D. i = 5 and j = 6
Answer» E.
Discussion
116.

Which two are valid constructors for Thread? Thread(Runnable r, String name) Thread() Thread(int priority) Thread(Runnable r, ThreadGroup g) Thread(Runnable r, int priority)

A. 1 and 3
B. 2 and 4
C. 1 and 2
D. 2 and 5
Answer» D. 2 and 5
Discussion
117.

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();
Answer» D. Thread t = new Thread(); x.run();
Discussion
118.

Which three are methods of the Object class? notify(); notifyAll(); isInterrupted(); synchronized(); interrupt(); wait(long msecs); sleep(long msecs); yield();

A. 1, 2, 4
B. 2, 4, 5
C. 1, 2, 6
D. 2, 3, 4
Answer» D. 2, 3, 4
Discussion
119.

switch(x) { default: System.out.println("Hello"); } Which two are acceptable types for x? byte long char float Short Long

A. 1 and 3
B. 2 and 4
C. 3 and 5
D. 4 and 6
Answer» B. 2 and 4
Discussion
120.

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.
Answer» B. "odd" will always be output.
Discussion
121.

public class While { public void loop() { int x= 0; while ( 1 ) /* Line 6 */ { System.out.print("x plus one is " + (x + 1)); /* Line 8 */ } } } Which statement is true?

A. There is a syntax error on line 1.
B. There are syntax errors on lines 1 and 6.
C. There are syntax errors on lines 1, 6, and 8.
D. There is a syntax error on line 6.
Answer» E.
Discussion
122.

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

A. 1, 2 and 4
B. 2, 5 and 6
C. 3, 4 and 7
D. 4, 5 and 7
Answer» C. 3, 4 and 7
Discussion
123.

Which two of the following methods are defined in class Thread? start() wait() notify() run() terminate()

A. 1 and 4
B. 2 and 3
C. 3 and 4
D. 2 and 4
Answer» B. 2 and 3
Discussion
124.

Which method must be defined by a class implementing the java.lang.Runnable interface?

A. void run()
B. public void run()
C. public void start()
D. void run(int priority)
Answer» C. public void start()
Discussion
125.

Which of the following will directly stop the execution of a Thread?

A. wait()
B. notify()
C. notifyall()
D. exits synchronized code
Answer» B. notify()
Discussion
126.

Which will contain the body of the thread?

A. run();
B. start();
C. stop();
D. main();
Answer» B. start();
Discussion
127.

Which method registers a thread in a thread scheduler?

A. run();
B. construct();
C. start();
D. register();
Answer» D. register();
Discussion
128.

Which of the following will not directly cause a thread to stop?

A. notify()
B. wait()
C. InputStream access
D. sleep()
Answer» B. wait()
Discussion
129.

Which class or interface defines the wait(), notify(),and notifyAll() methods?

A. Object
B. Thread
C. Runnable
D. Class
Answer» B. Thread
Discussion
130.

public class MyRunnable implements Runnable { public void run() { // some code here } } which of these will create and start this thread?

A. new Runnable(MyRunnable).start();
B. new Thread(MyRunnable).run();
C. new Thread(new MyRunnable()).start();
D. new MyRunnable().start();
Answer» D. new MyRunnable().start();
Discussion
131.

public class Test { public void foo() { assert false; /* Line 5 */ assert false; /* Line 6 */ } public void bar() { while(true) { assert false; /* Line 12 */ } assert false; /* Line 14 */ } } What causes compilation to fail?

A. Line 5
B. Line 6
C. Line 12
D. Line 14
Answer» E.
Discussion
132.

What will be the output of the program? public class Test { public static int y; public static void foo(int x) { System.out.print("foo "); y = x; } public static int bar(int z) { System.out.print("bar "); return y = z; } public static void main(String [] args ) { int t = 0; assert t &gt; 0 : bar(7); assert t &gt; 1 : foo(8); /* Line 18 */ System.out.println("done "); } }

A. bar
B. bar done
C. foo done
D. Compilation fails
Answer» E.
Discussion
133.

What will be the output of the program (when you run with the -ea option) ? public class Test { public static void main(String[] args) { int x = 0; assert (x &gt; 0) : "assertion failed"; /* Line 6 */ System.out.println("finished"); } }

A. finished
B. Compilation fails.
C. An AssertionError is thrown.
D. An AssertionError is thrown and finished is output.
Answer» D. An AssertionError is thrown and finished is output.
Discussion
134.

Which two cause a compiler error? float[ ] f = new float(3); float f2[ ] = new float[ ]; float[ ]f1 = new float[3]; float f3[ ] = new float[3]; float f5[ ] = {1.0f, 2.0f, 2.0f};

A. 2, 4
B. 3, 5
C. 4, 5
D. 1, 2
Answer» E.
Discussion
135.

Given a method in a protected class, what access modifier do you use to restrict access to that method to only the other members of the same class?

A. final
B. static
C. private
D. protected
E. volatile
Answer» D. protected
Discussion
136.

public class Test2 { public static int x; public static int foo(int y) { return y * 2; } public static void main(String [] args) { int z = 5; assert z &gt; 0; /* Line 11 */ assert z &gt; 2: foo(z); /* Line 12 */ if ( z &lt; 7 ) assert z &gt; 4; /* Line 14 */ switch (z) { case 4: System.out.println("4 "); case 5: System.out.println("5 "); default: assert z &lt; 10; } if ( z &lt; 10 ) assert z &gt; 4: z++; /* Line 22 */ System.out.println(z); } } which line is an example of an inappropriate use of assertions?

A. Line 11
B. Line 12
C. Line 14
D. Line 22
Answer» E.
Discussion
137.

Which is a valid declaration within an interface?

A. public static short stop = 23;
B. protected short stop = 23;
C. transient short stop = 23;
D. final void madness(short stop);
Answer» B. protected short stop = 23;
Discussion
138.

What is the widest valid returnType for methodA in line 3? public class ReturnIt { returnType methodA(byte x, double y) /* Line 3 */ { return (long)x / y * 2; } }

A. int
B. byte
C. long
D. double
Answer» E.
Discussion
139.

class A { protected int method1(int a, int b) { return 0; } } Which is valid in a class that extends class A?

A. public int method1(int a, int b) {return 0; }
B. private int method1(int a, int b) { return 0; }
C. public short method1(int a, int b) { return 0; }
D. static protected int method1(int a, int b) { return 0; }
Answer» B. private int method1(int a, int b) { return 0; }
Discussion
140.

Which one creates an instance of an array?

A. int[ ] ia = new int[15];
B. float fa = new float[20];
C. char[ ] ca = "Some String";
D. int ia[ ] [ ] = { 4, 5, 6 }, { 1,2,3 };
Answer» B. float fa = new float[20];
Discussion
141.

What is the most restrictive access modifier that will allow members of one class to have access to members of another class in the same package?

A. public
B. abstract
C. protected
D. synchronized
E. default access
Answer» F.
Discussion
142.

Which two of the following are legal declarations for nonnested classes and interfaces? final abstract class Test {} public static interface Test {} final public class Test {} protected abstract class Test {} protected interface Test {} abstract public class Test {}

A. 1 and 4
B. 2 and 5
C. 3 and 6
D. 4 and 6
Answer» D. 4 and 6
Discussion
143.

Which of the following class level (nonlocal) variable declarations will not compile?

A. protected int a;
B. transient int b = 3;
C. private synchronized int e;
D. volatile int d;
Answer» D. volatile int d;
Discussion
144.

Which of the following is/are legal method declarations? protected abstract void m1(); static final void m1(){} synchronized public final void m1() {} private native void m1();

A. 1 and 3
B. 2 and 4
C. 1 only
D. All of them are legal declarations.
Answer» E.
Discussion
145.

Which cause a compiler error?

A. int[ ] scores = {3, 5, 7};
B. int [ ][ ] scores = {2,7,6}, {9,3,45};
C. String cats[ ] = {"Fluffy", "Spot", "Zeus"};
D. boolean results[ ] = new boolean [] {true, false, true};
E. Integer results[ ] = {new Integer(3), new Integer(5), new Integer(8)};
Answer» C. String cats[ ] = {"Fluffy", "Spot", "Zeus"};
Discussion
146.

What will be the output of the program? class A { final public int GetResult(int a, int b) { return 0; } } class B extends A { public int GetResult(int a, int b) {return 1; } } public class Test { public static void main(String args[]) { B b = new B(); System.out.println("x = " + b.GetResult(0, 1)); } }

A. x = 0
B. x = 1
C. Compilation fails.
D. An exception is thrown at runtime.
Answer» D. An exception is thrown at runtime.
Discussion
147.

What will be the output of the program? public class A { void A() /* Line 3 */ { System.out.println("Class A"); } public static void main(String[] args) { new A(); } }

A. Class A
B. Compilation fails.
C. An exception is thrown at line 3.
D. The code executes with no output.
Answer» E.
Discussion
148.

What will be the output of the program? class Super { public int i = 0; public Super(String text) /* Line 4 */ { i = 1; } } class Sub extends Super { public Sub(String text) { i = 2; } public static void main(String args[]) { Sub sub = new Sub("Hello"); System.out.println(sub.i); } }

A. 0
B. 1
C. 2
D. Compilation fails.
Answer» E.
Discussion
149.

What will be the output of the program? public class Test { public int aMethod() { static int i = 0; i++; return i; } public static void main(String args[]) { Test test = new Test(); test.aMethod(); int j = test.aMethod(); System.out.println(j); } }

A. 0
B. 1
C. 2
D. Compilation fails.
Answer» E.
Discussion
150.

Which statement is true for the class java.util.HashSet?

A. The elements in the collection are ordered.
B. The collection is guaranteed to be immutable.
C. The elements in the collection are guaranteed to be unique.
D. The elements in the collection are accessed using a unique key.
Answer» D. The elements in the collection are accessed using a unique key.
Discussion