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Java Articles
Page 29 of 450
Can we overload methods of an interface in Java?
Polymorphism is the ability of an object to perform different actions (or, exhibit different behaviors) based on the context.Overloading is one of the mechanisms to achieve polymorphism where a class contains two methods with the same name and different parameters.Whenever you call this method the method body will be bound with the method call based on the parameters.ExampleIn the following Java program, the Calculator class has two methods with name addition the only difference is that one contains 3 parameters and the other contains 2 parameters.Here, we can call the addition method by passing two integers or three integers. Based ...
Read MoreHow to override only few methods of interface in Java?
Once you implement an interface from a concrete class you need to provide implementation to all its methods. If you try to skip implementing methods of an interface at compile time an error would be generated.Exampleinterface MyInterface{ public void sample(); public void display(); } public class InterfaceExample implements MyInterface{ public void sample(){ System.out.println("Implementation of the sample method"); } public static void main(String args[]) { InterfaceExample obj = new InterfaceExample(); obj.sample(); } }Compile-time errorInterfaceExample.java:5: error: InterfaceExample is not abstract and does not override abstract method display() ...
Read MoreIs it possible to override a Java method of one class in same?
When we have two classes where one extends another and if, these two classes have the same method including parameters and return type (say, sample) the method in the subclass overrides the method in the superclass.i.e. Since it is an inheritance. If we instantiate the subclass a copy of superclass’s members is created in the subclass object and, thus both methods are available to the object of the subclass.But if you call the method (sample), the sampling method of the subclass will be executed overriding the super class’s method.Exampleclass Super{ public static void sample(){ System.out.println("Method of ...
Read MoreWhen overriding clone method, why do we need to declare it as public in Java?
The clone() method belongs to the class named Object of the java.lang package, it accepts an object as a parameter creates and returns a copy of it.In order to use this method, you need to make sure that your class implements the Cloneable (marker) interface.Examplepublic class CloneExample implements Cloneable { private String name; private int age; public CloneExample(String name, int age){ this.name = name; this.age = age; } public void displayData(){ System.out.println("Name : "+this.name); System.out.println("Age : "+this.age); } public static void ...
Read MoreWhat happens when a subclass object is assigned to a superclass object in Java?
Converting one data type to others in Java is known as casting.If you convert a higher datatype to lower datatype, it is known as narrowing (assigning higher data type value to the lower data type variable).char ch = (char)5;If you convert a lower data type to a higher data type, it is known as widening (assigning lower data type value to the higher data type variable).Int i = 'c';Similarly, you can also cast/convert an object of one class type to others. But these two classes should be in an inheritance relation. Then, If you convert a Super class to subclass ...
Read MoreWhy subclass doesn't inherit the private instance variables of superclass in Java?
When you declare the instance variables of a class private, you cannot access them in another class if you try to do so a compile-time error will be generated.But, if you inherit a class that has private fields, including all other members of the class the private variables are also inherited and available for the subclass.But, you cannot access them directly, if you do so a compile-time error will be generated.Exampleclass Person{ private String name; public Person(String name){ this.name = name; } public void displayPerson() { System.out.println("Data of the Person ...
Read MoreHow to find the Strings within a text file in Java?
Following Java program accepts a String value from the user, verifies whether a file contains the given String and prints the number of occurrences of the word too.Exampleimport java.io.FileInputStream; import java.io.FileNotFoundException; import java.util.Scanner; public class FindingWordFromFile { public static void main(String args[]) throws FileNotFoundException { //Reading the word to be found from the user Scanner sc1 = new Scanner(System.in); System.out.println("Enter the word to be found"); String word = sc1.next(); boolean flag = false; int count = 0; System.out.println("Contents ...
Read MoreException Hierarchy in case of multiple catch blocks.
An exception is an issue (run time error) that occurred during the execution of a program. When an exception occurred the program gets terminated abruptly and, the code past the line that generated the exception never gets executed.Multiple exceptions in a codeWhenever we have a code that may generate more than one exception and if you need to handle them specifically you can use multiple catch blocks on a single try.try{ //code } catch(Exception1 ex1) { // } catch(Exception2 ex2) { // }Exampleimport java.util.Arrays; import java.util.Scanner; public class MultipleCatchBlocks { public static void main(String [] args) ...
Read MoreHow to read/write data from/to .properties file in Java?
The .properties is an extension in java which is used to store configurable application. It is represented by the Properties class in Java, you can store a properties file and read from it using the methods of this class. This class inherits the HashTable class.Creating a .properties file −To create a properties file −Instantiate the Properties class.Populate the created Properties object using the put() method.Instantiate the FileOutputStream class by passing the path to store the file, as a parameter.ExampleThe Following Java program creates a properties file in the path D:/ExampleDirectory/import java.io.FileOutputStream; import java.io.IOException; import java.util.Properties; public class CreatingPropertiesFile { ...
Read MoreCan I define more than one public class in a Java package?
No, while defining multiple classes in a single Java file you need to make sure that only one class among them is public. If you have more than one public classes a single file a compile-time error will be generated.ExampleIn the following example we have two classes Student and AccessData we are having both of them in the same class and declared both public.import java.util.Scanner; public class Student { private String name; private int age; Student(){ this.name = "Rama"; this.age = 29; } Student(String name, int age){ ...
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