Shruti Agarwal OOP Leave a comment

Covariant Return Type in Java

In this article, we will learn about covariant return types in Java. Before Java version 5.0, we could not change the return type of an overridden method but a new method was introduced in JDK 5.0, called covariant where we could change the return type of the overridden method. The return type must be non-primitive. (i.e., it should be a sub-type of the overridden class). Program:

class Employee {
    Employee work() {
        System.out.println("Employee");
        return this;
    }
}

class Manager extends Employee {
    @Override
    Manager work() {
        System.out.println("Manager");
        return this;
    }
}

class Main {
    public static void main(String[] args) {
        Manager obj = new Manager();
        obj.work();
    }
}

class Employee {

Employee work() {

System.out.println("Employee");

return this;

}

class Manager extends Employee {

@Override

Manager work() {

System.out.println("Manager");

return this;

}

class Main {

public static void main(String[] args) {

Manager obj = new Manager();

obj.work();

}

Output:

Manager

Manager

Explanation: In the above program, we created three classes: class ‘Employee’,

Shruti Agarwal OOP Leave a comment

Static Import in Java with Example

In this article, we will discuss static import in Java. Just as import statements are used to access a class without its package qualification. In a similar manner, static imports are used to access static members without their class qualification. Some basic static methods used with the class names are as follows: Math.sqrt(4): It is used to find the square root of the given number. Math.max(4, 2): It is used to find the maximum of the given numbers. Math.min(4, 2):

Shruti Agarwal OOP Leave a comment

Advantages and Disadvantages of Generics in Java

Generics in Java program was introduced in Java version 5. It is used to ensure the data type safety of objects. So, it constructs the code steady by detecting bugs at compile time. Why do we need generics in Java? When we write programs, errors occur. Some errors occur at run time while some errors occur at compile time. Those errors which occur at compile-time can be easily detected and rectified in the program. But, run time errors occur when

Shruti Agarwal Basic Leave a comment

Nested Switch in Java

In this article, we will discuss about nested switch in Java with examples. When a switch statement contains further switch statements inside it, then it is called a nested switch. Inside the nested switch statement, we can give multiple cases and a default case. The inner switch statement must be part of any outer case statement. We cannot use the inner switch statements outside the cases.

Shruti Agarwal Collection Leave a comment

TreeSet Vs TreeMap in Java

TreeSet is an implementation class of NavigableSet. In a TreeSet, duplicate as well as heterogenous (values of different data types) values are not allowed. If you’re trying to insert heterogeneous objects then it displays a ClassCastException. If the tree set exists, then we can insert a null value, and if the treeset doesn’t exist then we cannot insert a null value in it. All versions of Java below 6.0 allows insertion of null value, but all other versions show Null

Shruti Agarwal OOP Leave a comment

How to Access Variable From Another Class in Java?

In this article, we will learn how to access variable from another class in java. There are two ways to get variables from another class. Create an object of another class in the main class Extend another class in the main class Let us take a look at both these methods one by one with the help of sample programs. Method 1: Create Object of Another Class in Main Class In the following example, to access the variable ‘a’ of

Shruti Agarwal Basic Leave a comment

How to Get Filename Without Extension in Java

This article will talk about how to get filename without extension in Java language. The file utility method helps you to get rid of the file extension from the file name. Here is an example. Program:

class substring {
    public static void main(String[] args) {
        String fileName = "myfile.java";
        
        if(!fileName.contains("."))
            System.out.println("File Name = " + fileName);
        else {
            fileName = fileName.substring(0,fileName.lastIndexOf("."));
            System.out.println("File Name = " + fileName);
        }
    }
}

class substring {

public static void main(String[] args) {

String fileName = "myfile.java";

if(!fileName.contains("."))

System.out.println("File Name = " + fileName);

else {

fileName = fileName.substring(0,fileName.lastIndexOf("."));

System.out.println("File Name = " + fileName);

}

Output:

substring

substring

Explanation: We take a file named ‘myfile’ with the extension ‘.java’. Next, we check whether the filename contains ‘.’ or not. If it contains ‘.’, then go to the else part and get filename without an extension using substring() function. This

Shruti Agarwal OOP Leave a comment

Java Global Variables

In this article, we will see what is a global variable and how we can use this in our Java programs. In Java, all the functions and data members are declared inside a class and every declaration has to be done inside it. If we declare them outside the class, then they would not be accessible by the object of that class. Therefore, in Java, there is no such precise concept of global variables because these are described at the

« 1 2 3 4 5 … 26 »