Using Constructors : Constructor « Class Definition « Java Tutorial

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Java Tutorial » Class Definition » Constructor 
5. 2. 1. Using Constructors
  1. Every class must have at least one constructor.
  2. If there is no constructors for your class, the compiler will supply a default constructor(no-arg constructor).
  3. A constructor is used to construct an object.
  4. A constructor looks like a method and is sometimes called a constructor method.
  5. A constructor never returns a value
  6. A constructor always has the same name as the class.
  7. A constructor may have zero argument, in which case it is called a no-argument (or no-arg, for short) constructor.
  8. Constructor arguments can be used to initialize the fields in the object.

The syntax for a constructor is as follows.

constructorName (listOfArguments) {
    [constructor body]
}
public class MainClass {
  double radius;

  // Class constructor
  MainClass(double theRadius) {
    radius = theRadius;
  }
}
5. 2. Constructor
5. 2. 1. Using Constructors
5. 2. 2. The Default Constructor
5. 2. 3. Multiple Constructors
5. 2. 4. Calling a Constructor From a Constructor
5. 2. 5. Duplicating Objects using a Constructor
5. 2. 6. Class Initializer: during declaration
5. 2. 7. Order of constructor calls
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