Java 自定义类

Calculator2 的自定义类版 (Java基本语句与控制流)

Calculator2.java

public class Calculator2 {
public static void main(String[] args) {
    String s1 = MathHelper.getInput("Enter a numeric value: ");
    String s2 = MathHelper.getInput("Enter a numeric value: ");
    String op = MathHelper.getInput("Enter 1=Add, 2=Subtract , 3=Multiply, 4=Divide : ");

    int opInt = Integer.parseInt(op);
    double result = 0;

    switch (opInt){
        case  1:
             result = SimpleMath.addValues(s1, s2);
            break;
        case  2:
             result = SimpleMath.subtractValues(s1, s2);
            break;
        case  3:
             result = SimpleMath.multiplyValues(s1, s2);
            break;
        case  4:
             result = SimpleMath.divideValues(s1, s2);
            break;
        default:
            System.out.println("You entered an incorrect value:");
            return;
    }
    System.out.println("The answer is " + result);
}

}

MathHelper.java

import java.io.BufferedReader; import java.io.InputStreamReader;
/** * Created by Haseo on 5/31/2015. */ public class MathHelper { public static String getInput(String prompt) { BufferedReader stdin = new BufferedReader( new InputStreamReader(System.in));
    System.out.print(prompt);
    System.out.flush();

    try {
        return stdin.readLine();
    } catch (Exception e) {
        return "Error: " + e.getMessage();
    }
}

}

SimpleMath.java

public class SimpleMath {
public static double addValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    return d1 + d2;
}

public static double subtractValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    return d1 - d2;
}

public static double multiplyValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    return d1 * d2;
}

public static double divideValues(String s1, String s2) {
    double d1 = Double.parseDouble(s1);
    double d2 = Double.parseDouble(s2);
    return d1 / d2;
}

}

组织Java类

Organizing

Instance Methods (实例方法,对象)

参考 Difference between Static methods and Instance methods

Main.java

package com.bihell.olivepress;
import com.bihell.olivepress.olives.Olive; import com.bihell.olivepress.press.OlivePress;
public class Main {
public static void main(String[] args){
    Olive olive = new Olive();
    olive.crush();

    Olive[] olives = {new Olive(),new Olive(),new Olive()};
    OlivePress press = new OlivePress();
    press.getOil(olives);
}

}

Olive.java

package com.bihell.olivepress.olives;
public class Olive {
public void crush()  {
    System.out.println("ouch!");
}

}

OlivePress.java

package com.bihell.olivepress.press;
import com.bihell.olivepress.olives.Olive;
public class OlivePress { public void getOil(Olive[] olives) { for (Olive olive:olives) { olive.crush(); } } }

在Instance 变量中存储数据

Main.java

package com.bihell.olivepress;
import com.bihell.olivepress.olives.Olive; import com.bihell.olivepress.press.OlivePress;
import java.util.ArrayList;
public class Main {
public static void main(String[] args){

    ArrayList&lt;Olive&gt; olives = new ArrayList&lt;Olive&gt;();

    Olive olive;

    olive=new Olive();
    System.out.println(olive.name);
    olives.add(olive);

    olive = new Olive();
    System.out.println(olive.name);
    olives.add(olive);

    olive = new Olive();
    System.out.println(olive.name);
    olives.add(olive);

    OlivePress press = new OlivePress();
    press.getOil(olives);
}

}

Olive.java

package com.bihell.olivepress.olives;
public class Olive {
public String name = "Kalamata";
public String flavow = "Grassy";
public long color = 0x000000;
public int oil = 3;

public int crush()  {
    System.out.println("ouch!");
    return  oil;
}

}

OlivePress.java

import com.bihell.olivepress.olives.Olive;
import java.util.ArrayList;
public class OlivePress { public void getOil(ArrayList<Olive> olives) { int oil = 0;
    for (Olive olive:olives) {
       oil += olive.crush();
    }

    System.out.println("You got "+ oil+" units of oil");
}

}

Constructor Method(构造方法)

Main.java

package com.bihell.olivepress;
import com.bihell.olivepress.olives.Olive; import com.bihell.olivepress.press.OlivePress;
import java.util.ArrayList;
public class Main {
public static void main(String[] args){

    ArrayList&lt;Olive&gt; olives = new ArrayList&lt;Olive&gt;();

    Olive olive;

    olive=new Olive(2);
    System.out.println(olive.name);
    olives.add(olive);

    olive = new Olive(1);
    System.out.println(olive.name);
    olives.add(olive);

    olive = new Olive(2);
    System.out.println(olive.name);
    olives.add(olive);

    OlivePress press = new OlivePress();
    press.getOil(olives);
}

}

Olive.java

package com.bihell.olivepress.olives;
public class Olive {
public String name = "Kalamata";
public String flavow = "Grassy";
public long color = 0x000000;
public int oil = 3;

//构造方法
public Olive(){
    System.out.println("Constructor of "+ this.name);
}
//Alt+insert 可以自动生成构造函数
public Olive(int oil) {
    this.oil = oil;
}

public int crush()  {
    System.out.println("ouch!");
    return  oil;
}

}

OlivePress.java

package com.bihell.olivepress.press;
import com.bihell.olivepress.olives.Olive;
import java.util.ArrayList;
public class OlivePress { //为了让代码更清晰,可以习惯新的建立一个构造函数,即使什么都不做. public OlivePress() { }
public void getOil(ArrayList&lt;Olive&gt; olives) {
    int oil = 0;

    for (Olive olive:olives) {
       oil += olive.crush();
    }

    System.out.println("You got "+ oil+" units of oil");
}

}

Getter and Setter

按下Alt+Insert 可以自动生成Getter和Setter 我们选择oil

Main.java

package com.bihell.olivepress;
import com.bihell.olivepress.olives.Olive; import com.bihell.olivepress.press.OlivePress;
import java.util.ArrayList;
public class Main {
public static void main(String[] args){

    ArrayList&lt;Olive&gt; olives = new ArrayList&lt;Olive&gt;();

    Olive olive;

    olive=new Olive(2);
    System.out.println(olive.name);
    olives.add(olive);

    olive = new Olive(1);
    System.out.println(olive.name);
    olives.add(olive);

    olive = new Olive(2);
    System.out.println(olive.name);
    olives.add(olive);

    OlivePress press = new OlivePress();
    press.getOil(olives);

    System.out.println("You got "+ press.getTotalOil()+" units of oil");

    press.getOil(olives);

    System.out.println("You got "+ press.getTotalOil()+" units of oil");

}

}

Olive.java

package com.bihell.olivepress.olives;
public class Olive {
public String name = "Kalamata";
public String flavow = "Grassy";
public long color = 0x000000;

//利用Alt+Insert自动生成 getter and setter 
private int oil = 3;

public int getOil() {
    return oil;
}

public void setOil(int oil) {
    this.oil = oil;
}

//构造方法
public Olive(){
    System.out.println("Constructor of "+ this.name);
}
//Alt+insert 可以自动生成构造函数
public Olive(int oil) {
    setOil(oil);
}

public int crush()  {
    System.out.println("ouch!");
    return  oil;
}

}

OlivePress.java

package com.bihell.olivepress.press;
import com.bihell.olivepress.olives.Olive;
import java.util.ArrayList;
public class OlivePress {
private int totalOil=0;

public int getTotalOil() {
    return totalOil;
}

private void setTotalOil(int totalOil) {
    this.totalOil += totalOil;
}

public OlivePress() {
}

public void getOil(ArrayList&lt;Olive&gt; olives) {
    int oil = 0;

    for (Olive olive:olives) {
        oil += olive.crush();
    }

    setTotalOil(oil);

}

}