Java interviews and campus tests lean heavily on object oriented behaviour rather than API recall. This set covers inheritance and polymorphism, interfaces and abstract classes, the collections framework, exception handling, multithreading, string handling, and JVM basics such as garbage collection. Output based questions are included because they expose the gaps that theory questions hide.
What is the correct way to declare a constant in Java?
Answer: C
'const' is not a Java keyword. The correct convention for constants is public static final. Option D also works but C follows the standard convention.
Q.42Medium
Which statement about constructor overloading is true?
Answer: B
Constructors can be overloaded based on parameter count and types, but not on return type.
Q.43Easy
Which of the following is a valid variable declaration?
Answer: C
Variable names can contain letters, digits, underscores, and dollar signs, but cannot start with a digit or contain hyphens or dots.
Q.44Medium
What is the output of: System.out.println(5 % 2 + 3 * 2 - 1);?
Answer: A
Following operator precedence: 5%2=1, 3*2=6, then 1+6-1=6
Q.45Medium
Which of the following about static variables is incorrect?
Answer: C
Static variables are shared among ALL instances of a class, not individual copies per object.
Q.46Hard
What is the result of: int x = 5; System.out.println(x++ + ++x);?
Answer: B
x++ returns 5 (then increments to 6), ++x increments to 7 and returns 7. Sum = 5+7 = 12. Note: Actual result may vary due to JVM optimization but typically 11 or 12.
Q.47Medium
Which of the following cannot be inherited in Java?
Answer: C
Private members are not inherited. They remain accessible only within the class they are declared in.
Q.48Easy
What does the 'super' keyword do in Java?
Answer: B
The 'super' keyword is used to refer to parent class members and invoke parent class constructors.
Q.49Medium
Consider: class A { static int x = 5; } How many times is x initialized when you create multiple A objects?
Answer: B
Static variables are initialized only once when the class is first loaded into memory, regardless of object creation.
Q.50Hard
Which statement about Java's garbage collection is true?
Answer: B
Garbage collection in Java is non-deterministic. System.gc() is just a request, not a guarantee. Objects are eligible for GC when unreachable, but actual collection timing varies.
Q.51Easy
What is the purpose of the 'instanceof' operator?
Answer: B
The 'instanceof' operator is used to check if an object is an instance of a specific class or implements a specific interface.
Q.52Easy
What will be the output of: System.out.println(310);
Answer: B
Both operands are integers, so integer division is performed. Result is 3 (not 3.33). To get decimal, at least one operand must be float/double.
Q.53Easy
Consider the code: int x = 5; x += 3; What is the value of x?
Answer: B
The compound assignment operator += means x = x + 3. So 5 + 3 = 8.
Q.54Easy
Which of the following is a valid method name in Java?
Answer: B
Method names must start with a letter, underscore, or dollar sign. '_myMethod()' is valid. Names cannot start with digits, contain hyphens, or spaces.
Q.55Medium
What is the scope of a variable declared inside a method in Java?
Answer: B
Variables declared inside a method have local scope and are only accessible within that method. They are destroyed when the method returns.
Q.56Medium
Which of the following will result in a compilation error? class Test { public void method1() { } public void method1(int x) { } }
Answer: C
This is valid method overloading. Two methods with same name but different parameters (method signature) is allowed in Java.
Q.57Medium
What is the output of: System.out.println(true && false || true);
Answer: A
Evaluation: (true && false) || true = false || true = true. AND operator (&& has higher precedence than OR (||).
Q.58Medium
Which statement about method parameters is correct?
Answer: B
Java uses pass-by-value for all parameters. For objects, the value passed is the reference, but the reference itself is passed by value.
Q.59Medium
What is the difference between == and equals() in Java?
Answer: C
== compares object references (memory addresses). equals() method compares actual content/values and can be overridden.
