例子是：計算器，

方法一：是簡單的main實現

第一個類：

/**
?* 計算器，控制臺程序，輸入兩個數，一個運算符，得到結果
?* @author zhangqf
?*
?*/
public class calculate {
?? ?//用傳統的控制臺輸入的方法
?? ?public static void main(String[] args) {
?? ??? ?BufferedReader strin=new BufferedReader(new InputStreamReader(System.in));
?? ??? ?try {
?? ??? ??? ?System.out.println("請輸入一個數：");
?? ??? ??? ?String strFirst=strin.readLine();
?? ??? ??? ?double dbfirst=convertTool.StringToDouble(strFirst);
?? ??? ??? ?//System.out.println("第一個："+dbfirst);
?? ??? ??? ?
?? ??? ??? ?
?? ??? ??? ?System.out.println("請輸入第二個數：");
?? ??? ??? ?String strTwo=strin.readLine();
?? ??? ??? ?double dbTwo=convertTool.StringToDouble(strTwo);
?? ??? ??? ?//System.out.println("第二個："+dbTwo);
?? ??? ??? ?
?? ??? ??? ?System.out.println("請輸入操作符：");
?? ??? ??? ?String strOperate=strin.readLine();
?? ??? ??? ?//System.out.println("操作符："+strOperate);
?? ??? ??? ?
?? ??? ??? ?double dbResult=calculate.OperateResult(dbfirst, dbTwo, strOperate);
?? ??? ??? ?System.out.println("計算結果："+dbResult);
?? ??? ??? ?
?? ??? ?} catch (IOException e) {
?? ??? ??? ?System.out.println("您的輸入有錯："+e.getMessage());
?? ??? ??? ?e.printStackTrace();
?? ??? ?}
?? ??? ?
?? ??? ?
?? ?}
?? ?
?? ?
?? ?public static double OperateResult(double dbfirst,double dbTwo,String operate) {
?? ??? ?double result=0.0;
?? ??? ?switch (operate) {
?? ??? ?case "+":
?? ??? ??? ?result=dbfirst+dbTwo;
?? ??? ??? ?break;
?? ??? ?case "-":
?? ??? ??? ?result=dbfirst-dbTwo;
?? ??? ??? ?break;
?? ??? ?case "*":
?? ??? ??? ?result=dbfirst*dbTwo;
?? ??? ??? ?break;
?? ??? ?case "/":
?? ??? ??? ?if (dbTwo==0) {
?? ??? ??? ??? ?System.out.println("除數不能為0；");
?? ??? ??? ?}else{
?? ??? ??? ?result=dbfirst/dbTwo;
?? ??? ??? ?}
?? ??? ??? ?break;
?? ??? ?default:
?? ??? ??? ?System.out.println("輸入的符號不符合");
?? ??? ??? ?break;
?? ??? ?}
?? ??? ?
?? ??? ?return result;
?? ??? ?
?? ?}
??? }

第二個類：

public class convertTool {
?? ?public static double StringToDouble (String s) {
?? ??? ?if (s==null||s.length()==0)
?? ??? ??? ?return 0d;
?? ??? ?return Double.parseDouble(s);
?? ?}

}

?

第二種方法：簡單工廠模式：我自己理解就是用的：面向對象，繼承，封裝，多態

/**
?*1. 接口類
?* @author zhangqf
?*
?*/
public interface operationRestlt {
?? ?public double dbResule(double _dbFirst,double _dbTwo);
}

/**
?* 2.加號運算
?* @author zhangqf
?*
?*/
public class plusOperate implements operationRestlt{

?? ?@Override
?? ?public double dbResule(double _dbFirst, double _dbTwo) {
?? ??? ?double dbresult=_dbFirst+_dbTwo;
?? ??? ?return dbresult;
?? ?}
}

/**
?*3. 減號運算
?* @author zhangqf
?*/
public class subOperate implements operationRestlt{
?? ?@Override
?? ?public double dbResule(double _dbFirst, double _dbTwo) {
?? ??? ?double dbresult=_dbFirst-_dbTwo;
?? ??? ?return dbresult;
?? ?}
}

?

/**
?* 4.乘號運算
?* @author zhangqf
?*/
public class multipleOperate implements operationRestlt {

?? ?@Override
?? ?public double dbResule(double _dbFirst, double _dbTwo) {
?? ??? ?double dbresule=_dbFirst*_dbTwo;
?? ??? ?return dbresule;
?? ?}

}

/**
?* 5.除號運算
?* @author zhangqf
?*/
public class diviedOperate implements operationRestlt{

?? ?@Override
?? ?public double dbResule(double _dbFirst, double _dbTwo) {
?? ??? ?double dbresult=0d;
?? ??? ?if (_dbTwo==0) {
?? ??? ??? ?System.out.println("被除數不能為0");
?? ??? ?}else{
?? ??? ??? ? dbresult=_dbFirst/_dbTwo;
?? ??? ?}
?? ??? ?return dbresult;
?? ?}

}

//業務類

/**
?*6. 業務類
?* @author zhangqf
?*
?*/
public class operateAction {
?? ?
?? ?public static double operation(double _dbFirst,double _dbTwo,String oper) {
?? ??? ?double dbResult=0d;
?? ??? ?switch (oper) {
?? ??? ?case "+":
?? ??? ??? ?plusOperate plusOperate =new plusOperate();
?? ??? ??? ?dbResult=plusOperate.dbResule(_dbFirst, _dbTwo);
?? ??? ??? ?break;
?? ??? ?case "-":
?? ??? ??? ?subOperate operate=new subOperate();
?? ??? ??? ?dbResult=operate.dbResule(_dbFirst, _dbTwo);
?? ??? ??? ?break;
?? ??? ?case "*":
?? ??? ??? ?multipleOperate multipleOperate=new multipleOperate();
?? ??? ??? ?dbResult=multipleOperate.dbResule(_dbFirst, _dbTwo);
?? ??? ??? ?break;
?? ??? ?case "/":
?? ??? ??? ?diviedOperate diviedOperate=new diviedOperate();
?? ??? ??? ?dbResult=diviedOperate.dbResule(_dbFirst, _dbTwo);
?? ??? ??? ?break;

?? ??? ?default:
?? ??? ??? ?System.out.println("輸入的操作符不存在！");
?? ??? ??? ?break;
?? ??? ?}
?? ??? ?return dbResult;
?? ??? ?
?? ?}

}

import java.util.Scanner;
/**
?* 7.主程序調用運行
?* @author zhangqf
?*
?*/
public class main {
?? ?public static void main(String[] args) {
?? ??? ?Scanner scanner=new Scanner(System.in);
?? ??? ?System.out.println("請輸入第一個數：");
?? ??? ?double dbfirst=scanner.nextDouble();
?? ??? ?
?? ??? ?System.out.println("請輸入第二個數：");
?? ??? ?double dbtwo=scanner.nextDouble();
?? ??? ?
?? ??? ?System.out.println("請輸入操作符【+，-，*，/】");
?? ??? ?String operate=scanner.next();
?? ?
?? ??? ?double result=operateAction.operation(dbfirst,dbtwo,operate);
?? ??? ?System.out.println(result);
?? ??? ?
?? ?}

}

?

轉載于:https://www.cnblogs.com/zhangqf/p/6086792.html

《新程序員》：云原生和全面數字化實踐50位技術專家共同創作，文字、視頻、音頻交互閱讀

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