Computer Knowledge

Object-Oriented Programming

2,686 Questions

Object-oriented programming questions test core computer science concepts like classes, inheritance, polymorphism, and encapsulation. The focus includes Java program structures, method overloading, and memory allocation for objects. This topic is essential for technical sections in various recruitment tests.

Java class definitionsMethod overriding rulesPolymorphism conceptsGeneric type parametersMemory allocation in objects

Object-Oriented Programming Questions

Multiple choice technology programming languages 
public class MyOuter {
    public static class MyInner {
        public static void foo() {}
    }
}

which statement, if placed in a class other than MyOuter or MyInner, instantiates an instance of the nested class?

  1. MyOuter.MyInner m = new MyOuter.MyInner();

  2. MyOuter.MyInner mi = new MyInner();

  3. MyOuter m = new MyOuter(); MyOuter.MyInner mi = m.new MyOuter.MyInner();

  4. MyInner mi = new MyOuter.MyInner();
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For a static nested class, you use the fully qualified name with both outer and inner class names: 'new MyOuter.MyInner()'. Option B is missing 'MyOuter.' prefix. Option C incorrectly uses 'm.new' syntax (used for non-static inner classes). Option D is missing 'MyOuter.' prefix.

Multiple choice technology

OSH operator is an instance of a c++ class inheriting from

  1. Unix command line interface

  2. System dll

  3. APT_dump

  4. APT_Operator
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

OSH (Orchestrate Shell) operators in DataStage are instances of C++ classes that inherit from the APT_Operator base class. This base class provides the framework for all operator functionality. APT_dump is a debugging tool. The OSH operators are not related to Unix CLI or system DLLs.

Multiple choice technology mainframe

Using the Class Explorer to examine classes sorted alphabetically will allow you to view which type of inheritance?

  1. Directed Inheritance

  2. Pattern Inheritance

  3. Class Inheritance

  4. Genetic Inheritance
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In PegaRULES Process Commander, pattern inheritance relies on alphabetical class naming where classes inherit from parent classes that match their name pattern. The Class Explorer's alphabetical view reveals this pattern inheritance structure. Direct inheritance follows explicit parent-child relationships instead.

Multiple choice technology testing

Object Identification can be used to retrieve runtime values of object properties. State true or false

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Object Identification is a mechanism for uniquely identifying objects based on their properties during test recording and playback. It is not designed to retrieve runtime property values - that purpose is served by specific methods like GetROProperty. Object Identification focuses on property-based object recognition, not runtime value extraction.

Multiple choice technology packaged enterprise solutions

Which of the following is false about Private Ruleset

  1. System creates private ruleset automaticaly when needed

  2. instance of the Rule-Ruleset-Name class exists for a private RuleSet

  3. name of this RuleSet is the same as their Operator ID

  4. None
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A private ruleset (used for personal checkouts) is automatically managed by the system. Crucially, no actual Rule-Ruleset-Name instance is created in the database for a private ruleset, making the statement false and therefore the correct answer.

Multiple choice technology programming languages

We all know that constructors are nothing but methods in java. But, as all the methods are either static or non-static , Then, what is the type-access modifier for the constructor?

  1. static

  2. non-static

  3. special-mixed type

  4. not-defined
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Constructors in Java are not classified as static or non-static methods. They are a special type of block that initializes objects and have no explicit type-access modifier classification. While they behave like instance methods (they run on object creation), they are not technically methods and don't fit into the static/non-static binary.

Multiple choice technology programming languages

What is the concept Below??? 

class A  {
    int x=10;
};

class B extends A  {
    int x=100;
    show()     {
        System.out.println(x);
    }
    public static void main(String... s)  {
        B b1=new B();
        b1.show();
    }
};

The program will print 100. But the concept illustrated is----

  1. Data Shadowing

  2. Data Over-riding

  3. Data Obscuring

  4. None of the Above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In Java, declaring a field in a subclass with the same name as an inherited field in the superclass is called field hiding (or variable hiding). Since field hiding is not listed among the options, 'None of the Above' is correct, as overriding only applies to methods.

Multiple choice technology programming languages

Classes in Java cannot be made static.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Top-level classes in Java cannot be declared static. However, nested classes (inner classes) inside another class can be declared as static. Static nested classes are different from inner classes - they don't have access to instance members of the enclosing class.

Multiple choice technology programming languages

In Static inner classes, the data members and the member functions are by default static.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Static inner classes (nested static classes) behave like regular classes - their members are NOT static by default. They can have both instance and static members, just like any other Java class. The 'static' keyword on the class only means it doesn't require an instance of the enclosing class.

Multiple choice technology programming languages

Annonymous Inner classes are not possible within an Interface.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Anonymous inner classes can be created within interfaces in specific contexts. While interfaces cannot have instance initializers, anonymous classes can be defined inside static contexts like static field initialization or static blocks within the interface. This is a valid though rarely used Java feature.