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Method overloading

 

In Java (and C++), another factor forces the overloading of method names: the constructor. Because the constructor’s name is predetermined by the name of the class, there can be only one constructor name. But what if you want to create an object in more than one way? For example, suppose you build a class that can initialize itself in a standard way or by reading information from a file. You need two constructors, the default constructor and one that takes a String as an argument, which is the name of the file from which to initialize the object. Both are constructors, so they must have the same name—the name of the class. Thus, method overloading is essential to allow the same method name to be used with different argument types. And although method overloading is a must for constructors, it’s a general convenience and can be used with any method.

Here’s an example that shows both overloaded constructors and overloaded methods:

 

//: initialization/Overloading.java
// Demonstration of both constructor
// and ordinary method overloading.
import static net.mindview.util.Print.*;

class Tree {
  int height;
  Tree() {
    print("Planting a seedling");
    height = 0;
  }
  Tree(int initialHeight) {
    height = initialHeight;
    print("Creating new Tree that is " +
      height + " feet tall");
  }    
  void info() {
    print("Tree is " + height + " feet tall");
  }
  void info(String s) {
    print(s + ": Tree is " + height + " feet tall");
  }
}

public class Overloading {
  public static void main(String[] args) {
    for(int i = 0; i < 5; i++) {
      Tree t = new Tree(i);
      t.info();
      t.info("overloaded method");
    }
    // Overloaded constructor:
    new Tree();
  }	
} /* Output:
Creating new Tree that is 0 feet tall
Tree is 0 feet tall
overloaded method: Tree is 0 feet tall
Creating new Tree that is 1 feet tall
Tree is 1 feet tall
overloaded method: Tree is 1 feet tall
Creating new Tree that is 2 feet tall
Tree is 2 feet tall
overloaded method: Tree is 2 feet tall
Creating new Tree that is 3 feet tall
Tree is 3 feet tall
overloaded method: Tree is 3 feet tall
Creating new Tree that is 4 feet tall
Tree is 4 feet tall
overloaded method: Tree is 4 feet tall
Planting a seedling
*///:~

 

[Thinking in Java 110]

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