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2019/0514/Java_靜態類別+繼承特性

呼叫 ex: Math.PI
不能存取非Static類別成員
This這個參照是屬於動態方法 new 初始化物件 所以 static無法使用 static 屬於編譯時就存在了 new則是new之後才存在

展示動態物件內靜態屬性值
靜態方法只能讀取靜態參數值
動態靜態無法互相呼叫參照
使用靜態方法方式
動態方法new完後應該靜態參數就可以存取
但還是會報錯應該要在 static方法內存取

package com.example.java;
public class EmployeeS {
private static int count = 0; // number of Employees created
private String firstName;
private String lastName;
public Date birthDate;
public Date hireDate;
public EmployeeS(String firstName, String lastName,Date birthDate, Date hireDate) {
this.firstName = firstName;
this.lastName = lastName;
this.birthDate = birthDate;
this.hireDate = hireDate;
++count;
System.out.printf("EmployeeS 物件建立成功 : %s %s; EmployeeS物件數量 = %d%n", firstName, lastName, count);
}
public String getFirstName() {
String strTemp = String.valueOf(this.count);
return firstName+strTemp;
}
public String getLastName() {
return lastName;
}
public static int getCount() {
// String s1= firstName;
// String s2;
// s2 = getFirstName();
return count;
}
public String toString() {
return String.format("%s,%s-雇用日期: %s-出生日期: %s", lastName, firstName, hireDate, birthDate);
}
}

package com.example.java;
public class EmployeeSTest {
public static void main(String[] args) {
// TODO 自動產生的方法 Stub
System.out.printf("新增員工前, EmployeeS物件數量: %d%n", EmployeeS.getCount());
Date birth = new Date(7, 24, 2005);
Date hire = new Date(3, 12, 2016);
EmployeeS e1 = new EmployeeS("李", "連杰", birth, hire);
EmployeeS e2 = new EmployeeS("甄", "子丹", birth, hire);
System.out.printf("%n新增員工後, EmployeeS物件數量:%n");
System.out.printf("呼叫 EmployeeS.getCount(): %d%n", EmployeeS.getCount());
System.out.printf("%n員工 1: %s %s%n員工2: %s %s%n", e1.getFirstName(), e1.getLastName(), e2.getFirstName(),
e2.getLastName());
System.out.println(e1);
}
}

Import 在 c#就是using

package com.example.java;
import static java.lang.Math.*;
//import static java.lang.Math.sqrt;
//import static java.lang.Math.ceil;
public class StaticImportTest {
public static void main(String[] args) {
// TODO 自動產生的方法 Stub
System.out.printf("呼叫 Math.sqrt,sqrt(900.0) = %.1f%n", sqrt(900.0));
System.out.printf("呼叫 Math.ceil,ceil(-9.8) = %.1f%n", ceil(-9.8));
System.out.printf("呼叫 Math.E,E = %f%n", java.lang.Math.E);
System.out.printf("呼叫 Math.PI,PI = %f%n", java.lang.Math.PI);
}
}

Is a relationship

Has a relationship

越子代特徵會越明顯越清楚跟界門綱目科屬種很像

一般化往上移 ( 通用
特性化往下移

Private 必須要在同一個 class 裡面
Protected 要有繼承關係或同個packge

package com.example.java;
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)
{
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("Commission rate must be > 0.0 and < 1.0");
this.commissionRate = commissionRate;
}
public double getCommissionRate()
{
return commissionRate;
}
public double earnings()
{
return commissionRate * grossSales;
}
@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", firstName, lastName,
"身分證字號", idNumber,
"每周銷售金額", grossSales,
"佣金比例", commissionRate,
"薪資",this.earnings());
}
}

操控CommissionEmployee類別鑄造物件並操控物件進行方法
但其實是準備跟Employee類別做一般化的父類別

package com.example.java;
public class CommissionEmployeeTest {
public static void main(String[] args) {
// TODO 自動產生的方法 Stub
CommissionEmployee employee01 = new CommissionEmployee("劉", "德華", "A123456789", 10000, .06);
CommissionEmployee employee02 = new CommissionEmployee("陳", "立農", "A123456789", 5000, .1);
System.out.println("以下呼叫 Get Method 取回員工資料:");
System.out.printf("%n%s %s%n", "姓:", employee01.getFirstName());
System.out.printf("%s %s%n", "名:", employee01.getLastName());
System.out.printf("%s %s%n", "身分證字號:", employee01.getIdNumber());
System.out.printf("%s %.2f%n", "銷售金額:", employee01.getGrossSales());
System.out.printf("%s %.2f%n", "佣金比例:", employee01.getCommissionRate());
employee01.setGrossSales(15000);
employee01.setCommissionRate(.65);
System.out.printf("%n%s:%n%n%s%n", "更新員工資料後,呼叫 toString Method 取回員工資料:", employee01);
System.out.printf("%n%s:%n%n%s%n", "第二位員工資料", employee02.toString());
}
}

Java 什麼是多載(Overload), 覆寫(Override), 多型(Polymorphism)
Java Platform SE 7
在實作一個子類別 不一樣的地方只有紅色的地方

建構子 方法 程式碼幾乎一樣

設計繼承架構 從兩個都是繼承object轉成其中一個為父類別,
(BasePlusCommissionEmployee、CommissionEmployee

java super c# - Google Search
Google

package com.example.java;
public class CommissionEmployeeExtV1 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 CommissionEmployeeExtV1(String firstName, String lastName, String idNumber, double grossSales, double commissionRate)
{
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 commissionRate * grossSales;
}
@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", firstName, lastName,
"身分證字號", idNumber,
"每周銷售金額", grossSales,
"佣金比例", commissionRate,
"薪資",this.earnings());
}
}

package com.example.java;
public class BasePlusCommissionEmployeeExtV1 extends CommissionEmployeeExtV1{
private double baseSalary; //底薪
public BasePlusCommissionEmployeeExtV1(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()
{
return baseSalary + (super.getCommissionRate() * super.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", super.getFirstName(), super.getLastName(),
"身分證字號", super.getIdNumber(),
"每周銷售金額", getGrossSales(),
"佣金比例", getCommissionRate(),
"底薪金額", baseSalary);
}
}

package com.example.java;
public class BasePlusCommissionEmployeeExtV1Test {
public static void main(String[] args) {
// TODO 自動產生的方法 Stub
BasePlusCommissionEmployeeExtV1 employee01 = new BasePlusCommissionEmployeeExtV1("劉", "德華", "A123456789", 10000, .06,1000);
CommissionEmployeeExtV1 employee02 = new CommissionEmployeeExtV1("陳", "立農", "A123456789", 5000, .1);
System.out.println("以下呼叫 Get Method 取回員工資料:");
System.out.printf("%n%s %s%n", "姓:", employee01.getFirstName());
System.out.printf("%s %s%n", "名:", employee01.getLastName());
System.out.printf("%s %s%n", "身分證字號:", employee01.getIdNumber());
System.out.printf("%s %.2f%n", "銷售金額:", employee01.getGrossSales());
System.out.printf("%s %.2f%n", "佣金比例:", employee01.getCommissionRate());
System.out.printf("%s %.2f%n", "底薪金額:", employee01.getBaseSalary());
employee01.setGrossSales(15000);
employee01.setCommissionRate(0.1);
employee01.setBaseSalary(2000);
System.out.printf("%n%s:%n%n%s%n", "更新員工資料後,呼叫 toString Method 取回員工資料:", employee01);
System.out.printf("總薪資:"+String.valueOf(employee01.earnings()));
System.out.println("\n\n領獎金員工資料:");
System.out.printf("%n%s:%n%n%s%n", "呼叫 toString Method 取回員工資料:", employee02);
}
}

經過一系列以上的操作可以看到繼承後的程式碼少了非常少 (重複的都在父類別了
而且修改只要改源頭不需要一個檔案一個檔案改
接著 V2版本
保留封裝特性但同時又能存取父類別參數
孫代也更好的可以存取參數

package com.example.java;
public class CommissionEmployeeExtV2 extends Object{
protected final String firstName;
protected final String lastName;
protected final String idNumber;
protected double grossSales;
protected double commissionRate; // 佣金,抽庸的比例
public CommissionEmployeeExtV2(String firstName, String lastName, String idNumber, double grossSales, double commissionRate)
{
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 commissionRate * grossSales;
}
@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", firstName, lastName,
"身分證字號", idNumber,
"每周銷售金額", grossSales,
"佣金比例", commissionRate,
"薪資",this.earnings());
}
}

package com.example.java;
public class BasePlusCommissionEmployeeExtV2 extends CommissionEmployeeExtV2 {
protected double baseSalary; // 底薪
public BasePlusCommissionEmployeeExtV2(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 baseSalary + (commissionRate * grossSales);
}
@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", firstName, lastName,
"身分證字號", idNumber,
"每周銷售金額", grossSales,
"佣金比例", commissionRate,
"底薪金額", baseSalary);
}
}

package com.example.java;
public class BasePlusCommissionEmployeeExtV2Test {
public static void main(String[] args) {
// TODO 自動產生的方法 Stub
BasePlusCommissionEmployeeExtV2 employee01 = new BasePlusCommissionEmployeeExtV2("劉", "德華", "A123456789", 10000, .06,1000);
CommissionEmployeeExtV2 employee02 = new CommissionEmployeeExtV2("陳", "立農", "A123456789", 5000, .1);
System.out.println("以下呼叫 Get Method 取回員工資料:");
System.out.printf("%n%s %s%n", "姓:", employee01.getFirstName());
System.out.printf("%s %s%n", "名:", employee01.getLastName());
System.out.printf("%s %s%n", "身分證字號:", employee01.getIdNumber());
System.out.printf("%s %.2f%n", "銷售金額:", employee01.getGrossSales());
System.out.printf("%s %.2f%n", "佣金比例:", employee01.getCommissionRate());
System.out.printf("%s %.2f%n", "底薪金額:", employee01.getBaseSalary());
employee01.setGrossSales(15000);
employee01.setCommissionRate(0.1);
employee01.setBaseSalary(2000);
System.out.printf("%n%s:%n%n%s%n", "更新員工資料後,呼叫 toString Method 取回員工資料:", employee01);
System.out.printf("總薪資:"+String.valueOf(employee01.earnings()));
System.out.println("\n\n領獎金員工資料:");
System.out.printf("%n%s:%n%n%s%n", "呼叫 toString Method 取回員工資料:", employee02);
}
}
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#Java類別&物件
##Static 類別成員
##靜態類別匯入
#繼承
##直接間接父類別
##類別在使用上有兩種狀態
##向上轉型
##繼承-存取權
##在不夠熟悉時 通常是實作兩個子類別最後再把相同之處往上搬制做父類別
##建構子不會被繼承
##不標記@Override也會複寫但最好要加上去
##繼承的使用
#子類別呼叫父類別建構式
##初始化new父輩實體變數(參數) super , c#裡面是base
##繼承重點
##參數使用保護繼承的問題