Constructor Overloading in Java Geeksfor. Geeks. Prerequisite Constructor, Overloading in java. In addition to overloading methods, we can also overload constructors in java. Overloaded constructor is called based upon the parameters specified when new is executed. When do we need Constructor Overloading Sometimes there is a need of initializing an object in different ways. This can be done using constructor overloading. For example, Thread class has 8 types of constructors. If we do not want to specify anything about a thread then we can simply use default constructor of Thread class, however if we need to specify thread name, then we may call the parameterized constructor of Thread class with a String args like this. Thread t new Thread My. Thread. Let us take an example to understand need of constructor overloading. Consider the following implementation of a class Box with only one constructor taking three arguments. An example class to understand need of. Core Java Interview Questions and Answers for Beginner, Advanced Experienced programmers from my 10 years of java programming and interviewing experience. Sample Interview Questions Interview Questions. This page lists some common interview questions for software engineers. Questions. Click on the question to see its. This is a Java Program to implement a queue using linked list. Queue is a particular kind of abstract data type or collection in which the entities in the collection. Constructor Program In Java' title='Constructor Program In Java' />Boxdouble w, double h, double d. As we can see that the Box constructor requires three parameters. This means that all declarations of Box objects must pass three arguments to the Box constructor. For example, the following statement is currently invalid. Box ob new Box. Since Box requires three arguments, its an error to call it without them. Constructor Program In Java' title='Constructor Program In Java' />Suppose we simply wanted a box object without initial dimension, or want to to initialize a cube by specifying only one value that would be used for all three dimensions. From the above implementation of Box class these options are not available to us. These types of problems of different ways of initializing an object can be solved by constructor overloading. Below is the improved version of class Box with constructor overloading. Java program to illustrate. When a new instance of an object is created, the constructor method is called. Examples of how to create constructor methods in Java are discussed here. Java Serialization Learn Java in simple and easy steps starting from basic to advanced concepts with examples including Java Syntax Object Oriented Language. Java is a programming language created by James Gosling from Sun Microsystems Sun in 1991. The target of Java is to write a program once and then run this program. Java Language and Virtual Machine Specifications Java SE 9 The Java Language Specification, Java SE 9 Edition HTML PDF. The Java Virtual Machine Specification, Java. Constructor Overloading. Boxdouble w, double h, double d. Boxdouble len. width height depth len. Test. public static void mainString args. Box mybox. 1 new Box1. Box mybox. 2 new Box. Box mycube new Box7. System. out. println Volume of mybox. System. out. println Volume of mybox. System. out. println Volume of mycube is vol. Volume of mybox. 1 is 3. The Sims 3 Base Game Iso. Volume of mybox. 2 is 1. Volume of mycube is 3. Using this in constructor overloadingthis reference can be used during constructor overloading to call default constructor implicitly from parameterized constructor. Please note, this should be the first statement inside a constructor. Java program to illustrate role of this in. Constructor Overloading. No specified. Boxdouble w, double h, double d, int num. No num. constructor used when no dimensions specified. No specified. Boxint num. No num. public static void mainString args. No. Box box. 1 new Box1. System. out. printlnbox. As we can see in the above program that we called Boxint num constructor during object creation using only box number. By using this statement inside it, the default constructorBox is implicitly called from it which will initialize dimension of Box with 1. Note The constructor calling should be first statement in the constructor body. For example, following fragment is invalid and throws compile time error. No num. Constructor call must be the first. ERROR. Important points to be taken care while doing Constructor Overloading Constructor calling must be the first statement of constructor in Java. If we have defined any parameterized constructor, then compiler will not create default constructor. Recursive constructor calling is invalid in java. Constructors overloading vs Method overloading. Strictly speaking, constructor overloading is somewhat similar to method overloading. If we want to have different ways of initializing an object using different number of parameters, then we must do constructor overloading as we do method overloading when we want different definitions of a method based on different parameters. This article is contributed by Gaurav Miglani. If you like Geeksfor. Geeks and would like to contribute, you can also write an article using contribute. See your article appearing on the Geeksfor. Geeks main page and help other Geeks. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. Panda Internet Security Serial Number on this page.