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Java Interview Questions and Answers


Constructor Interview Questions | Java Interview Questions and Answers


Introduction

In this article, we will be discussing Java constructor interview questions and answers.

What is the purpose of constructors in Java?

Constructors are used to initializing the object. For example, if you create an Employee class and add a constructor to this class then it will be initialized as follows:

```java

public class Employee {

private String name;

private int age;

public Employee(String name, int age) { this(); this.name = name; this.age = age; } //end of constructor definition section

How many types of constructors are there in Java?

There are two types of constructors in Java:

  • No-argument constructor. This type of constructor has no parameters and is used to initialize the fields or objects that are created by this method. For example, if you have an Employee class with only one field called name, then you can initialize it with a no-argument constructor like this:

public Employee(String name) { this.name = name; }

What is the difference between a constructor and a method in java?

  • You should know the difference between a constructor and a method in Java. A constructor is used to initialize an object, whereas methods are used to perform some operation on it. For example, consider this class:

import java.util.*; public class ConstructorTest { private String name; public ConstructorTest(String name) { this .name = name; } public static void main(String[] args) throws Exception { new ConstructorTest("Bob"); new ConstructorTest("Ravi"); System.out.println("Created 2 objects"); } } In this program, you can see how two objects are created using different constructors with different parameter values named "Bob" and "Ravi". The output will be:

Created 2 objects

Why is Java constructor called constructor?

The constructor of an object is called when the object is created. It's used to initialize the fields and constructors of a class, so they are ready to use when you instantiate your instance of that class.

Unix/Linux: The first time you create a program or script, it will run as root(superuser). On Unix operating systems, there are three levels of permissions: user level, group level and superuser (root). When a program runs with these permissions on Unix/Linux systems then it can access all files within that directory tree including any other subdirectory in its path as well as files located outside those directories but inside another filesystem such as CD-ROMs or USB drives etcetera!

Does constructor return any value in Java, and if yes, then what type of value it returns?

In Java, a constructor is called when an object is created. In other words, it's called before main() method. This can be done by using new keyword.

A constructor is a special method or block that gets executed when an object of its class/type is created or instantiated inside that class/type. The syntax for creating your own constructor in Java looks like this:

class MyClass { public MyClass() {} }

You can also initialize your variables in the constructor instead of having them initialized outside the class (as they are by default). This will make sure that all fields are correctly initialized even if you need to use some method later on which requires their values

Is constructor inherited in Java?

You can’t inherit a constructor. A constructor is used to create an object, which means that it doesn’t have any parent class.

Inheritance is used to create a super class and sub class in Java programming language. A constructor can be inherited by creating another constructor that has the same name as the original one but with additional parameters added on top of it.

You may ask why we need to inherit constructors if there is no inheritance between them? The answer lies in handling different types of data structures differently across classes; for example: StringBuffer vs StringBuilder – The first one takes one string variable while second one takes two variables (one for each side).

Can we override constructors in Java? If not, why is that so ?

In Java, constructors are not inherited. This means that you cannot declare a constructor for an object of another class or any other method or variable that does not have a default value. This also means that if you want to call one of your own methods from within an overridden constructor, it will be declared as private.

If you do want to override the default constructor in Java, then doing so would be considered bad practice because it changes how code works around it (i.e., if someone calls any function which has been defined by calling some other function). Overloading constructors is not recommended as well since each time one is called by another object's class (or even outside), there may be side effects like memory leaks and possible errors due to using different memory locations than what was expected when writing them down initially!

Can we overload constructors in Java? If yes, how?

Constructor is a special type of method. It is not inherited and can only be invoked on an object once. The name of the constructor must be the same as the class name, but you can use different parameter lists for your constructors by using overloaded constructors.

Can anyone provide me an example of how to overload a constructor using three parameters (int, float, double)in java ?

The signature of a constructor is defined as the combination of its name, parameter types, and the return type. The following example shows how to define two constructors with different signatures:

public class MyClass {

public MyClass() { } // default constructor

public MyClass(int i) { } // constructor with int parameter (i)

Learn about constructors and become a better candidate for jobs.

To understand what a constructor is, it is first important to know that a constructor is used to create objects. Constructors are called before an object is created and initialize the instance variables of your class. They also call the superclass constructor so that it can initialize itself properly.

You can use constructors to call other constructors or even other methods in your own class but they cannot be invoked directly by themselves.

For example: * You could write this method: public void Foo(). This method causes a new instance of FooClass to be created and then calls its "public" super("Foo") method. The call returns immediately without waiting for another invocation from outside this method. * If we want something like this functionality (having multiple invocations), then we would have several nested calls inside our original Foo() method.<br

Conclusion

In this article, I have tried to explain the various types of constructors in Java and have given a few examples. If you have any queries related to this topic, do write to me.