CtrlAiHub

1. What will be printed as the output of the following program?

public class testincr
                {
                public static void main(String args[])
                {
                int i = 0;
                i = i++ + i;
                System.out.println(“I = ” +i);
                }
                }
                

1. I = 1
2. I = 0
3. I = 2
4. I = 3 5. Compile-time Error

3.What is the output of the following program?

                public class testmeth
                {
                static int i = 1;
                public static void main(String args[])
                {
                System.out.println(i+” , “);
                m(i);
                System.out.println(i);
                }
                public void m(int i)
                {
                i += 2;
                }
                }
                
               

1. 1 , 3
2.3 , 1
3.1 , 1
4.1 , 0 5.None of the above

4. Which Map class should be most popular in a multi-threading environment, considering performance constraint ?

1. HashSet
2.CopyOnWriteMap
3. ConcurrentHashMap
4. ConcurrentMap

5. Which allows the removal of elements from a collection?

1. Enumeration
2. Iterator
3. Both
4. None of the above

6.Which offers the best performance?

1. TreeMap
2.HashMap
3. LinkedHashMap
4. None of the above

7.Which of these is the most popularly used class as a key in a HashMap?

1. String
2.Double
3.Integer
4.All of the above

8. Iterator returned by ArrayList is?

1. Fail-fast
2. Fail-safe
3. None of the above
4. All of the above

9.Which of the following statements about Java Threads is correct?

1. Java threads don’t allow parts of a program to be executed in parallel
2. Java is a single-threaded language
3. Java’s garbage collector runs as a high priority thread
4. Ready, running and sleeping are three states that a thread can be in during its life cycle

10.Among these expressions, which is(are) of type String?

1. “0”
2. “ab” + “cd”
3. ‘0’
4. Both (A) and (B) above (e) (A), (B) and (C) above

11.Consider the two methods (within the same class)?

public static int foo(int a, String s)
{
s = “Yellow”;
a=a+2;
return a;
}
public static void bar()
{
int a=3;
String s = “Blue”;
a = foo(a,s);
System.out.println(“a=”+a+” s=”+s);
}
public static void main(String args[])
{
bar();
}

            

1. a = 3 s = Blue
2. a = 5 s = Yellow
3. a = 3 s = Yellow
4. a = 5 s = Blue

12.The method setValue assigns the value of i to the instance field value. What could you write for the implementation of setValue?

public class MyClass
{
private int value;
public void setValue(int i){ / code / }
// Other methods…
}

            

1. value = i;
2. this.value = i;
3. value == i;
4. Both (A) and (B) and above (e) (A), (B) and (C) above.

13.To instantiate MyClass, you would write?

public class MyClass
{
public MyClass(){/code/}
// more code…
}

            

1.MyClass mc = MyClass();
2.MyClass mc = new MyClass();
3. MyClass mc = MyClass;
4. The constructor of MyClass should be defined as, public void MyClass(){/code/}.

14.What is the output of the following code:?

class eq
{
public static void main(String args[])
{
String s1 = “Hello”;
String s2 = new String(s1);
System.out.println(s1==s2);
}
}

            

1. false
2. true
3. 0
4. 1

15.Use the following declaration and initialization to evaluate the Java expressions?

                int a = 2, b = 3, c = 4, d = 5;
                float k = 4.3f;
                System.out.println( – -b * a + c *d – -);
                

1. 21
2. 26
3. 28
4. 24