A java constructor has the same name as the name of the class. Constructor does not have any return type. It's also not of void type.
Java provides a default constructor which takes no arguments and performs no special actions or initializations, when no explicit constructors are provided.
Constructors may include parameters of various types. When the constructor is invoked using the new operator, the types must match those that are specified in the constructor definition.
- Every class must have at least one constructor.
- If there is no constructors for your class, the compiler will supply a default constructor(no-arg constructor).
- A constructor is used to construct an object.
- A constructor looks like a method and is sometimes called a constructor method.
- A constructor never returns a value
- A constructor always has the same name as the class.
- A constructor may have zero argument, in which case it is called a no-argument (or no-arg, for short) constructor.
- Constructor arguments can be used to initialize the fields in the object.
Example 1:
public class MainClass {
double radius;
MainClass() {
}
// Class constructor
MainClass(double theRadius) {
radius = theRadius;
}
}
Example 2:
public class MainClass {
double radius;
// Class constructor
MainClass(double theRadius) {
radius = theRadius;
}
}