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Object Oriented Programming Articles
Page 225 of 588
Importance of HashSet in Java
The HashSet use Hashing to manipulate data. Let us see an example − Example import java.util.*; public class Demo{ private final String f_str, l_str; public Demo(String f_str, String l_str){ this.f_str = f_str; this.l_str = l_str; } public boolean equals(Object o){ if (o instanceof Demo) return true; Demo n = (Demo)o; return n.f_str.equals(f_str) && n.l_str.equals(l_str); } public static void main(String[] args){ ...
Read MoreHow can we implement a custom iterable in Java?
An Iterable interface is defined in java.lang package and introduced with Java 5 version. An object that implements this interface allows it to be the target of the "for-each" statement. This for-each loop is used for iterating over arrays and collections. An Iterable interface can also be implemented to create custom behavior. Syntax public interface Iterable Example import static java.lang.String.format; import java.util.*; // Person class class Person { private String firstName, lastName; private int age; public Person(){ } public Person(String firstName, String lastName, int age) { this.firstName = firstName; ...
Read MoreCan I import same package twice? Will JVM load the package twice at runtime?
In Java classes and interfaces related to each other are grouped under a package. Package is nothing but a directory storing classes and interfaces of a particular concept. For example, all the classes and interfaces related to input and output operations are stored in java.io package. Creating a Package You can group required classes and interfaces under one package just by declaring the package at the top of the Class/Interface (file) using the keyword package as − Example public class Sample{ public void demo(){ System.out.println("This is a method of the sample class"); } ...
Read MoreHow many ways to make an object eligible for GC in Java?
The process of destroying unreferenced objects is called a Garbage Collection(GC). Once an object is unreferenced it is considered as an unused object, hence JVM automatically destroys that object. There are various ways to make an object eligible for GC. By nullifying a reference to an object We can set all the available object references to "null" once the purpose of creating an object is served. Example public class GCTest1 { public static void main(String [] args){ String str = "Welcome to TutorialsPoint"; // String object referenced by variable str and it is not eligible for GC yet. ...
Read MoreCan we declare an interface with in another interface in java?
An interface in Java is a specification of method prototypes. Whenever you need to guide the programmer or, make a contract specifying how the methods and fields of a type should be you can define an interface. To create an object of this type you need to implement this interface, provide body for all the abstract methods of the interface and obtain the object of the implementing class. Nested Interfaces Java allows declaring interfaces within another interface, these are known as nested interfaces. While implementing you need to refer to the nested interface as outerInterface.nestedInterface. Example In the following Java example, we have an interface with ...
Read MoreHow can we implement a timer thread in Java?
The Timer class schedules a task to run at a given time once or repeatedly. It can also run in the background as a daemon thread. To associate Timer with a daemon thread, there is a constructor with a boolean value. The Timer schedules a task with fixed delay as well as a fixed rate. In a fixed delay, if any execution is delayed by System GC, the other execution will also be delayed and every execution is delayed corresponding to previous execution. In a fixed rate, if any execution is delayed by System GC then 2-3 execution happens consecutively to ...
Read MoreWhat is the importance of a StringWriter in Java?
The StringWriter class is s subclass of Writer class and it writes the String to an output stream. To write a string, this character stream collects the string into a string buffer and then constructed a string. The buffer of StringWriter automatically grows according to data. The important methods of StringWriter class are write(), append(), getBuffer(), flush() and close(). Syntax public class StringWriter extends Writer Example import java.io.*; public class StringWriterTest { public static void main(String args[]) { String str = "Welcome to Tutorials Point"; try { ...
Read MoreWhat is the importance of Runtime class in Java?
The java.lang.Runtime class is a subclass of Object class, can provide access to various information about the environment in which a program is running. The Java run-time environment creates a single instance of this class that is associated with a program. The Runtime class does not have any public constructors, so a program cannot create its own instances of the class. A program must call the getRuntime() method to get a reference to the current Runtime object. The important methods of Runtime class are addShutdownHook(), exec(), exit(), freeMemory(), gc(), halt() and load(). Syntax public class Runtime extends Object Example public class RuntimeTest { ...
Read MoreWhat are the steps to read static members in a Java class?
A static variable gets created at the time of class loading even before the execution of a static block and the purpose of the static block is to assign value to the static variables. A static variable stores a value that is shared between all instances of the class it is defined in and a static block is a section of code that gets executed when class is first loaded. If we want any logic that needs to be executed at the time of class loading that logic needs to place inside the static block so that it will be executed ...
Read MoreWhy an interface cannot implement another interface in Java?
An interface cannot implement another interface in Java. An interface in Java is essentially a special kind of class. Like classes, the interface contains methods and variables. Unlike classes, interfaces are always completely abstract. An interface is defined just like a class except for the keyword interface in place of a class, the variables are declared in an interface are static and final and the methods are defined in an interface are public abstract methods. An interface can extend any number of interfaces but one interface cannot implement another interface, because if any interface is implemented then its methods must be defined and ...
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