Java Tutorial/Class Definition/Method Overloading

Demonstration of both constructor and ordinary method overloading

class MyClass {
  int height;
  MyClass() {
    System.out.println("Planting a seedling");
    height = 0;
  }
  MyClass(int i) {
    System.out.println("Creating new Tree that is " + i + " feet tall");
    height = i;
  }
  void info() {
    System.out.println("Tree is " + height + " feet tall");
  }
  void info(String s) {
    System.out.println(s + ": Tree is " + height + " feet tall");
  }
}
public class MainClass {
  public static void main(String[] args) {
    MyClass t = new MyClass(0);
    t.info();
    t.info("overloaded method");
    // Overloaded constructor:
    new MyClass();
  }
}

Creating new Tree that is 0 feet tall
Tree is 0 feet tall
overloaded method: Tree is 0 feet tall
Planting a seedling

Method Overloading

Java allows you to have multiple methods having the same name, as long as each method accept different sets of argument types. In other words, in our example, it is legal to have these two methods in the same class.

public String printString(String string)
public String printString(String string, int offset)

Methods with differing type signatures are overloaded - not overridden.

class A {
  int i, j;
  A(int a, int b) {
    i = a;
    j = b;
  }
  void show() {
    System.out.println("i and j: " + i + " " + j);
  }
}
class B extends A {
  int k;
  B(int a, int b, int c) {
    super(a, b);
    k = c;
  }
  void show(String msg) {
    System.out.println(msg + k);
  }
}
class Override {
  public static void main(String args[]) {
    B subOb = new B(1, 2, 3);
    subOb.show("This is k: "); // this calls show() in B
    subOb.show(); // this calls show() in A
  }
}

Overloading based on the order of the arguments

public class MainClass {
  static void print(String s, int i) {
    System.out.println("String: " + s + ", int: " + i);
  }
  static void print(int i, String s) {
    System.out.println("int: " + i + ", String: " + s);
  }
  public static void main(String[] args) {
    print("String first", 11);
    print(99, "Int first");
  }
}

String: String first, int: 11
int: 99, String: Int first

Pass long parameters to overloading method

It is legal to have these two methods in the same class.

public class MainClass {
  public int printNumber(int i) {
      return i*2;
  }
  public long printNumber(long i) {
      return i*3;
  }
  public static void main(String[] args) {
  }
}

Primitives and overloading

public class MainClass {
  void f1(char x) {
    System.out.println("f1(char)");
  }
  void f1(byte x) {
    System.out.println("f1(byte)");
  }
  void f1(short x) {
    System.out.println("f1(short)");
  }
  void f1(int x) {
    System.out.println("f1(int)");
  }
  void f1(long x) {
    System.out.println("f1(long)");
  }
  void f1(float x) {
    System.out.println("f1(float)");
  }
  void f1(double x) {
    System.out.println("f1(double)");
  }
  void f2(char x) {
    System.out.println("f2(char)");
  }
  void f2(byte x) {
    System.out.println("f2(byte)");
  }
  void f2(short x) {
    System.out.println("f2(short)");
  }
  void f2(int x) {
    System.out.println("f2(int)");
  }
  void f2(long x) {
    System.out.println("f2(long)");
  }
  void f2(float x) {
    System.out.println("f2(float)");
  }
  void f3(char x) {
    System.out.println("f3(char)");
  }
  void f3(byte x) {
    System.out.println("f3(byte)");
  }
  void f3(short x) {
    System.out.println("f3(short)");
  }
  void f3(int x) {
    System.out.println("f3(int)");
  }
  void f3(long x) {
    System.out.println("f3(long)");
  }
  void f4(char x) {
    System.out.println("f4(char)");
  }
  void f4(byte x) {
    System.out.println("f4(byte)");
  }
  void f4(short x) {
    System.out.println("f4(short)");
  }
  void f4(int x) {
    System.out.println("f4(int)");
  }
  void f5(char x) {
    System.out.println("f5(char)");
  }
  void f5(byte x) {
    System.out.println("f5(byte)");
  }
  void f5(short x) {
    System.out.println("f5(short)");
  }
  void f6(char x) {
    System.out.println("f6(char)");
  }
  void f6(byte x) {
    System.out.println("f6(byte)");
  }
  void f7(char x) {
    System.out.println("f7(char)");
  }
  void testDouble() {
    double x = 0;
    System.out.println("double argument:");
    f1(x);
    f2((float) x);
    f3((long) x);
    f4((int) x);
    f5((short) x);
    f6((byte) x);
    f7((char) x);
  }
  public static void main(String[] args) {
    MainClass p = new MainClass();
    p.testDouble();
  }
}

double argument:
  f1(double)
  f2(float)
  f3(long)
  f4(int)
  f5(short)
  f6(byte)
  f7(char)

Using Method Overloading

A method"s name with the types and sequence of the parameters form the method"s signature

public class MainClass {
  public void print(int a) {
    System.out.println(a);
  }
  public void print(String a) {
    System.out.println(a);
  }
}

Using overloaded methods to print array of different types

public class MainClass {
  // method printArray to print Integer array
  public static void printArray(Integer[] inputArray) {
    // display array elements
    for (Integer element : inputArray)
      System.out.printf("%s ", element);
    System.out.println();
  }
  // method printArray to print Double array
  public static void printArray(Double[] inputArray) {
    // display array elements
    for (Double element : inputArray)
      System.out.printf("%s ", element);
    System.out.println();
  }
  // method printArray to print Character array
  public static void printArray(Character[] inputArray) {
    // display array elements
    for (Character element : inputArray)
      System.out.printf("%s ", element);
    System.out.println();
  }
  public static void main(String args[]) {
    // create arrays of Integer, Double and Character
    Integer[] integerArray = { 1, 2, 3, 4, 5, 6 };
    Double[] doubleArray = { 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7 };
    Character[] characterArray = { "H", "E", "L", "L", "O" };
    System.out.println("Array integerArray contains:");
    printArray(integerArray); // pass an Integer array
    System.out.println("\nArray doubleArray contains:");
    printArray(doubleArray); // pass a Double array
    System.out.println("\nArray characterArray contains:");
    printArray(characterArray); // pass a Character array
  }
}

Array integerArray contains:
1 2 3 4 5 6 
Array doubleArray contains:
1.1 2.2 3.3 4.4 5.5 6.6 7.7 
Array characterArray contains:
H E L L O