2019/0520/繼承&存取權特性+java作業四+字符串格式化+多形+抽象類別
2019/0520/
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2019/0520/
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類別變數改為protected 保護
就不用用方法存取變數
但壞處就是沒辦法用商業邏輯驗證變數
且子類父類會相依性提高
可以跟V2比較
把V2變數改為
然後需要變數屬性的部分都運存取方法得到
維護修改的範圍限制在建構式與存取方法
用呼叫的就會達到上述維護修改範圍限制的好處
super() 是一種連鎖方法 能夠呼叫直接父類別的建構式
才能在子類別繼續執行變數檢查等等的內容
Google search java se 8 object
新增一個CommissionEmployeeExtV3Test 測試V3改完後功能是否正常
package com.example.java;
public class BasePlusCommissionEmployeeExtV3 extends CommissionEmployeeExtV3 {
private double baseSalary; // 底薪
public BasePlusCommissionEmployeeExtV3(String firstName, String lastName, String idNumber, double grossSales,double commissionRate, double baseSalary) {
super(firstName, lastName, idNumber, grossSales, commissionRate);
if (baseSalary < 0.0)
throw new IllegalArgumentException("底薪金額必須 >= 0.0");
this.baseSalary = baseSalary;
}
public void setBaseSalary(double baseSalary) {
if (baseSalary < 0.0)
throw new IllegalArgumentException("底薪金額必須 >= 0.0");
this.baseSalary = baseSalary;
}
public double getBaseSalary() {
return baseSalary;
}
@Override
public double earnings() {
// grossSales = -5000.0;
return getBaseSalary() + (super.getCommissionRate() * super.getGrossSales());
}
@Override
public String toString() {
return String.format("%s %n %s: %.2f" ,
super.toString(),
"底薪金額", getBaseSalary());
}
}
檔案不確定有沒有上傳但其實就是測試以上類別的方法 set 與get
特殊性邏輯往子類丟
通用性邏輯往父類丟
package com.example.java;
//實作Shape形狀類別
//公開存取 繼承於 Class Object
//https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html
public class Shape extends Object {
//私有存取 雙精度浮點數 double 型態變數表示 area 面積
private double area;
//公開存取 shape(無參數) 建構子
//this指建構式自身
//https://developer.mozilla.org/zh-TW/docs/Web/JavaScript/Reference/Operators/this
//https://openhome.cc/Gossip/Java/This.html
//http://peimei0808.pixnet.net/blog/post/125557313-%5Bjava%5D-java%E4%B8%AD%E5%A6%82%E4%BD%95%E4%BD%BF%E7%94%A8%E3%80%8Cthis%E3%80%8D%E5%8F%8A%E5%85%B6%E5%8A%9F%E7%94%A8%E4%B9%8B%E4%BB%8B%E7%B4%B9
public Shape() {
this.area = 0;
}
//公開存取 shape(double型態area參數) 建構式
//當area參數小於0時拋出錯誤訊息物件參數為 "面積必須 >=0"
public Shape(double area) {
if (area < 0)
throw new IllegalArgumentException("面積必須 >= 0");
this.area = area;
}
//公開存取 反傳值double型態 getArea(無參數) 方法
//回傳 area變數
public double getArea() {
return area;
}
//公開存取 沒有反傳值 getArea(double型態area參數) 方法
//當area參數小於0時拋出錯誤訊息物件參數為 "面積必須 >=0"
public void setArea(double area) {
if (area < 0)
throw new IllegalArgumentException("\"面積必須為大於或等於0\"");
this.area = area;
}
//覆載Override object.toString 靜態類別方法
//https://wayne265265.pixnet.net/blog/post/115533452-%E3%80%90%E6%95%99%E5%AD%B8%E3%80%91override-%E8%88%87-overload-%E7%9A%84%E5%B7%AE%E5%88%A5
//%s : %.2f%n 為字符串格式
@Override
public String toString() {
return String.format("%s : %.2f%n", "此形狀的面積為", getArea());
}
}
package com.example.java;
//實作Rectangle長方形類別
//公開存取 繼承於 Class Shape
public class Rectangle extends Shape {
//私有存取 雙精度浮點數 double 型態變數 表示 length 長度
//私有存取 雙精度浮點數 double 型態變數 表示 width 寬度
private double length;
private double width;
//公開存取 shape(double型態length長度, double型態width寬度) 建構子
//當Rectangle的參數小於0時拋出錯誤訊息物件參數為"長度 、寬度皆必須大於等於0"
//並將建構式帶入的參數指給私有存取的域外變數
public Rectangle(double length, double width) {
if ((length < 0) || (width < 0))
throw new IllegalArgumentException("長度 、寬度皆必須大於等於0");
this.length = length;
this.width = width;
ComputeArea();
}
//公開存取 double型態反傳值 getLength(無參數) 方法
public double getLength() {
return length;
}
//公開存取 無反傳值 setLength(double型態length參數) 方法
//當長度小於零時反傳"長度必須大於等於 0"
public void setLength(double length) {
if (length < 0)
throw new IllegalArgumentException("長度必須大於等於 0");
this.length = length;
}
//公開存取 double型態反傳值 getWidth(無參數) 方法
public double getWidth() {
return width;
}
//公開存取 無反傳值 setWidth(double型態width參數) 方法
//當長度小於零時反傳"寬度必須大於 0"
public void setWidth(double width) {
if (width < 0)
throw new IllegalArgumentException("寬度必須大於 0");
this.width = width;
}
//公開存取 double型態反傳值 ComputeArea(無參數) 方法
//用getLength方法取得長度與getWidth方法取得寬度做*乘法運算將運算值傳入直接父輩方法super.setArea中
public double ComputeArea() {
super.setArea(getLength() * getWidth());
return getArea();
}
//覆載
@Override
public String toString()
{
return String .format("%s : %.2f%n","形狀為矩形，面積為",getArea() );
}
}
package com.example.java;
//實作Triangle三角形類別
//公開存取 繼承於 Class Shape
public class Triangle extends Shape {
//私有存取 雙精度浮點數 double 型態變數 表示 base 底邊長度
//私有存取 雙精度浮點數 double 型態變數 表示 height 高度
private double base;
private double height;
//公開存取 Triangle(double型態base底邊長度, double型態height高度) 建構子
//當Triangle的參數小於0時拋出錯誤訊息物件參數為"底邊 、高度皆必須大於等於0"
//並將建構式帶入的參數指給私有存取的域外變數
public Triangle(double base, double height) {
if ((base < 0) || (height < 0))
throw new IllegalArgumentException("底邊 、高度皆必須大於等於0");
this.base = base;
this.height = height;
ComputeArea();
}
//公開存取 double型態反傳值 getBase(無參數) 方法
public double getBase() {
return base;
}
//公開存取 無反傳值 setBase(double型態base參數) 方法
//當長度小於零時反傳"底邊必須大於0"
public void setBase(double base) {
if (base < 0)
throw new IllegalArgumentException("底邊必須大於0");
this.base = base;
}
//公開存取 double型態反傳值 getHeight(無參數) 方法
public double getHeight() {
return height;
}
//公開存取 無反傳值 getHeight(double型態height參數) 方法
//當長度小於零時反傳"高度必須大於等於0"
public void getHeight(double height) {
if (height < 0)
throw new IllegalArgumentException("高度必須大於等於0");
this.height = height;
}
//公開存取 double型態反傳值 ComputeArea(無參數) 方法
//用getBase方法取得底邊長度與getHeight方法取得高度做*乘法後除與2運算將運算值傳入直接父輩方法super.setArea中
public double ComputeArea() {
setArea(getBase() * getHeight() / 2);
return getArea();
}
//覆載
@Override
public String toString()
{
return String .format("%s : %.2f%n","形狀為三角形，面積為",getArea() );
}
}
Hw4Test.java ( 使用上述類別與方法 且有多型?
宣告物件變數 建構式初始化時順便給予參數
接著印出
接著宣告一個物件陣列塞剛剛的物件進去
For印不同參數版本的物件值出來
package com.example.java;
import com.example.java.Shape;
public class Hw4Test {
public static void main(String[] args) {
// TODO 自動產生的方法 Stub
//建構三個物件並給予參數
Shape sp1 = new Shape(11);
Rectangle rt1 = new Rectangle(6,0);
Triangle ta1 = new Triangle(6, 5.0);
//利用物件使用方法並給予參數
sp1.setArea(5);
// rt1.ComputeArea();
//利用靜態方法印出以上物件
System.out.println(sp1);
System.out.println(rt1);
System.out.println(ta1);
// 以下為多型示範 ( 結果如同以上 )
// Shape[] shapeArray = new Shape[3];
// shapeArray[0] = sp1;
// shapeArray[1] = rt1;
// shapeArray[2] = ta1;
//
// for(int i=0;i<shapeArray.length;i++)
// {
// System.out.println(shapeArray[i]);
// }
}
}
https://ctf-wiki.github.io/ctf-wiki/pwn/linux/fmtstr/fmtstr_intro/
https://www.google.com/search?q=java+tostring+%E6%A0%BC%E6%98%AF&oq=java+tostring+%E6%A0%BC%E6%98%AF&aqs=chrome..69i57.9777j0j4&sourceid=chrome&ie=UTF-8
雇員更上層的父類別?
直接間接處理相同父類別的物件
子可以參考父但父不可參考子
子類別物件可以拿去父用
但父不可以參考子 除非向下轉型 ( 整數轉換成浮點數
強制型別轉換 向下轉型 父轉子 在塞到子類別物件變數
得到呼叫子類別方法能力
子類別是一種父類別 但父類別不是一種子類別
一個父類別有很多個子類別的話，會呼叫出正確的版本ex
xxxx.toString()
不會呼叫到
Object.toString
package polymorphism;
public class CommissionEmployee extends Object{
private final String firstName;
private final String lastName;
private final String idNumber;
private double grossSales;
private double commissionRate; // 佣金，抽庸的比例
public CommissionEmployee(String firstName, String lastName, String idNumber, double grossSales, double commissionRate)
{
super();
if (grossSales < 0.0)
throw new IllegalArgumentException("銷售金額必須 >= 0.0");
if (commissionRate <= 0.0 || commissionRate >= 1.0)
throw new IllegalArgumentException("佣金比例必須 > 0.0 and < 1.0");
this.firstName = firstName;
this.lastName = lastName;
this.idNumber = idNumber;
this.grossSales = grossSales;
this.commissionRate = commissionRate;
}
public String getFirstName()
{
return firstName;
}
public String getLastName()
{
return lastName;
}
public String getIdNumber()
{
return idNumber;
}
public void setGrossSales(double grossSales)
{
if (grossSales < 0.0)
throw new IllegalArgumentException("銷售金額必須 >= 0.0");
this.grossSales = grossSales;
}
public double getGrossSales()
{
return grossSales;
}
public void setCommissionRate(double commissionRate)
{
if (commissionRate <= 0.0 || commissionRate >= 1.0)
throw new IllegalArgumentException("佣金比例必須 > 0.0 and < 1.0");
this.commissionRate = commissionRate;
}
public double getCommissionRate()
{
return commissionRate;
}
public double earnings()
{
return getCommissionRate() * getGrossSales();
}
@Override
public String toString()
{
return String.format("%s: %s %s%n%s: %s%n%s: %.2f%n%s: %.2f %n%s: %.2f" ,
"領佣金的員工姓名", getFirstName(), getLastName(),
"身分證字號", getIdNumber(),
"每周銷售金額", getGrossSales(),
"佣金比例", getCommissionRate(),
"總佣金",getCommissionRate() * getGrossSales());
}
}
package polymorphism;
public class BasePlusCommissionEmployee extends CommissionEmployee {
private double baseSalary; // 底薪
public BasePlusCommissionEmployee(String firstName, String lastName, String idNumber, double grossSales,double commissionRate, double baseSalary) {
super(firstName, lastName, idNumber, grossSales, commissionRate);
if (baseSalary < 0.0)
throw new IllegalArgumentException("底薪金額必須 >= 0.0");
this.baseSalary = baseSalary;
}
public void setBaseSalary(double baseSalary) {
if (baseSalary < 0.0)
throw new IllegalArgumentException("底薪金額必須 >= 0.0");
this.baseSalary = baseSalary;
}
public double getBaseSalary() {
return baseSalary;
}
@Override
public double earnings() {
// grossSales = -5000.0;
return getBaseSalary() + (super.getCommissionRate() * super.getGrossSales());
}
@Override
public String toString() {
return String.format("%s %n %s: %.2f" ,
super.toString(),
"底薪金額", getBaseSalary());
}
}
package polymorphism;
public class WeekSalaryPlusCommissionEmployee extends CommissionEmployee {
private double weekSalary; // 周薪
public WeekSalaryPlusCommissionEmployee(String firstName, String lastName, String idNumber, double grossSales,double commissionRate, double weekSalary) {
super(firstName, lastName, idNumber, grossSales, commissionRate);
if (weekSalary < 0.0)
throw new IllegalArgumentException("周薪金額必須 >= 0.0");
this.weekSalary = weekSalary;
}
public void setWeekSalary(double weekSalary) {
if (weekSalary < 0.0)
throw new IllegalArgumentException("周薪金額必須 >= 0.0");
this.weekSalary = weekSalary;
}
public double getWeekSalary() {
return weekSalary;
}
@Override
public double earnings() {
return getWeekSalary() + (super.getCommissionRate() * super.getGrossSales());
}
@Override
public String toString() {
return String.format("%s%n %s %n %s: %.2f" , "領周薪加獎金的員工",
super.toString(), "周薪金額", getWeekSalary() );
}
}
package polymorphism;
public class PolymorphismTest {
public static void main(String[] args) {
// TODO 自動產生的方法 Stub
// BasePlusCommissionEmployee employee01 = new BasePlusCommissionEmployee("劉", "德華", "A123456789", 10000, .06,1000);
// CommissionEmployee employee02 = new CommissionEmployee("陳", "立農", "A123456789", 5000, .1);
// CommissionEmployee employee03 = new CommissionEmployee("周", "子瑜", "A111111111", 6000, .06);
// BasePlusCommissionEmployee employee04 = new BasePlusCommissionEmployee ("吳", "奕帆", "A222222222", 1000, .08,5000);
//
// System.out.printf("%n%s:%n%n%s%n", "第 1 位員工薪資資料", employee01.toString());
// System.out.printf("%n%s:%n%n%s%n", "第 2 位員工薪資資料", employee02.toString());
// System.out.printf("%n%s:%n%n%s%n", "第 3 位員工薪資資料", employee03.toString());
// System.out.printf("%n%s:%n%n%s%n", "第 4 位員工薪資資料", employee04.toString());
CommissionEmployee employeeArray[] = new CommissionEmployee[5];
employeeArray[0] = new BasePlusCommissionEmployee("劉", "德華", "A123456789", 10000, .06, 1000);
employeeArray[1] = new CommissionEmployee("陳", "立農", "A123456789", 5000, .1);
employeeArray[2] = new CommissionEmployee("周", "子瑜", "A111111111", 6000, .06);
employeeArray[3] = new BasePlusCommissionEmployee("吳", "奕帆", "A222222222", 1000, .08, 5000);
employeeArray[4] = new WeekSalaryPlusCommissionEmployee("韓", "國魚", "A333333333", 2000, .05, 500);
for(int i = 0; i < employeeArray.length ;i++)
{
System.out.printf("%n%s%d%s:%n%n%s%n", "第 ",i+1," 位員工薪資資料", employeeArray[i].toString());
}
}
}
父類別子用與多參數型
就算再設計設備的時候也要考慮未來可能擴充元件與特定控制方法，所以一定要有多型，ex 薪水計算方法現行公司指有兩種，難道未來不會有別種或是更多種?
指拿來定義 無法用new配置實體物件
抽象類別的 子類別一定要實作屬於子類別版本的方法
讓子符合父的一定規範
規範架構 擴展的範圍
