[contoh] Interface

Ya, seperti biasa,..
ini adalah contoh-contoh dari interface.

import javax.swing.JOptionPane;

interface mycomparableee{

boolean greaterThan(Object obj);

boolean lessThan(Object obj);

boolean equal(Object obj);

}

interface Constants{

int min=10;

int max=100;

}

class FourDigitsNumber implements Constants, mycomparableee {

  private int value;

  public FourDigitsNumber(int value) {

  /*atur agar nilai yang diinputkan dalam

                 constructor hanya berada di antara min - max

    */

    this.value=value;

}

  /*tambahkan method get untuk mengakses value*/

  /*overriding method greaterThan*/

  public int getValue(){

  return value;

  }

  public boolean greaterThan(Object obj) {

    /*casting from superclass to subclass*/

    FourDigitsNumber number = (FourDigitsNumber)obj;

    return ( value > number.getValue() );

  }

  public boolean lessThan(Object obj) {

    /*casting from superclass to subclass*/

    FourDigitsNumber number = (FourDigitsNumber)obj;

    return ( value < number.getValue() );

  }

  public boolean equal(Object obj) {

    /*casting from superclass to subclass*/

    FourDigitsNumber number = (FourDigitsNumber)obj;

    return ( value == number.getValue() );

  }

  /*lengkapi overriding method interface*/

  }

 class ExInterface {

  public static void main(String [] args) {

        int value;

        String str=JOptionPane.showInputDialog("Masukkan nilai : ");

        value=Integer.parseInt(str);

        System.out.println("nilai anda: "+value);

        if ((value > 10) & (value < 100))

            System.out.println("true");

        else

            System.out.println("false");

  }

  }

import javax.swing.*;

interface Induk {

  double LuasSegi3(double a, double t);

  double LuasSegi4(double s);

  double Lingkaran(double r);

}

interface Constants{

  double phi = 3.14;

}

class Luas implements Induk,Constants{   

  double a, t, s, r, LuasSegi3, LuasSegi4, Lingkaran;

  Luas(double a,double t,double s,double r) {

    this.a = a;

    this.t = t;

        this.s = s;

    this.r = r;

  }

  public double LuasSegi3(double a, double t) {

    return (0.5 * a * t);

  }

  public double LuasSegi4(double s) {

    return (s * s);

  }

  public double Lingkaran(double r) {

    return (phi * r * r);

  }

  public void CetakHasil() {

    System.out.println("LuasSegi3 = "+LuasSegi3(a,t));

        System.out.println("LuasSegi4 = "+LuasSegi4(s));

        System.out.println("Lingkaran = "+Lingkaran(r));

  }

}

class LuasBidang{

  public static void main(String[] args)  { 

         double a, t, s, r, LuasSegi3, LuasSegi4, Lingkaran;

     System.out.println("Masukkan nilai alas : ");

     a=Integer.parseInt(JOptionPane.showInputDialog(null,"Input nilai alasnya ","Input",JOptionPane.QUESTION_MESSAGE));

     System.out.println(+a);

     System.out.println("Masukkan nilai tinggi : ");

     t=Integer.parseInt(JOptionPane.showInputDialog(null,"Input nilai tingginya ","Input",JOptionPane.QUESTION_MESSAGE));

     System.out.println(+t);

         System.out.println("Masukkan nilai sisinya : ");

     s=Integer.parseInt(JOptionPane.showInputDialog(null,"Input nilai sisinya ","Input",JOptionPane.QUESTION_MESSAGE));

     System.out.println(+s);

     System.out.println("Masukkan nilai jari2 : ");

     r=Integer.parseInt(JOptionPane.showInputDialog(null,"Input nilai jarinya ","Input",JOptionPane.QUESTION_MESSAGE));

     System.out.println(+r);

    Luas Luas1 = new Luas(a,t,s,r);

    Luas1.CetakHasil();

  }

}

Nah ini yang terakhir.

import javax.swing.*;

interface MtkDasar {

  double tambah(int a, int b);

  double kurang(int a, int b);

}

class Pecahan implements MtkDasar{      

  private int a;

  private int b;

  Pecahan(int a,int b) {

    this.a = a;

    this.b = b;

  }

  public double tambah(int a, int b) {

    return (a + b);

  }

  public double kurang(int a, int b) {

    return (a - b);

  }

  public void cetakHasil() {

    System.out.println("a + b = " + tambah(a, b));

    System.out.println("a - b = " + kurang(a, b));

  }

}

class CobaPecahan { 

  public static void main(String[] args) {

    int a;

  int b;

    System.out.println("Masukkan nilai a : ");

    a = Integer.parseInt(JOptionPane.showInputDialog(null,"Input nilai a ","Input",JOptionPane.QUESTION_MESSAGE));

    System.out.println(+a);

    System.out.println("Masukkan nilai b : ");

    b = Integer.parseInt(JOptionPane.showInputDialog(null,"Input nilai b ","Input",JOptionPane.QUESTION_MESSAGE));

    System.out.println(+b);

  Pecahan HasilHitung = new Pecahan(a,b);         

    HasilHitung.cetakHasil();       

  }          

}