Java Bigdecimal類

Question

這是一項家庭作業，我正在設計一個興趣計算器。我需要使用BigDecimal類，但無法弄清楚如何以貨幣或百分比形式輸出。我不完全確定要問什麼問題，但我要發佈兩個代碼BigDecimal類代碼，另一個以我需要的方式顯示輸出，但不使用BigDecimal。任何建議感激。

import java.util.Scanner; 

    import java.math.*; 

    public class project3a 
    { 


     public static void main(String[] args) 
     { 
      System.out.println("Welcome to the interest calculator"); 
      System.out.println(); 


      // create a scanner object and start while loop    
      Scanner sc = new Scanner(System.in); 
      String choice ="y"; 
      while (choice.equalsIgnoreCase("y")) 
      { 

      //Get input from user 
      System.out.print("Enter Loan amount: "); 
      double Loanamount = sc.nextDouble(); 

      System.out.print("Enter Interest Rate: "); 
      double interestrate = sc.nextDouble(); 

      //calculate results  
      double Interest = Loanamount * interestrate; 

      //format 
      BigDecimal decimalLoanamount = new BigDecimal(Double.toString (Loanamount)); 
      decimalLoanamount = decimalLoanamount.setScale(2, RoundingMode.HALF_UP); 
      BigDecimal decimalinterestrate = new BigDecimal(Double.toString(interestrate)); 
      BigDecimal decimalInterest = new BigDecimal (Double.toString(Interest)); 
      decimalInterest = decimalInterest.setScale(2,RoundingMode.HALF_UP); 

      //Display results 
      System.out.println("Loan amount: " + decimalLoanamount); 
      System.out.println("Interest rate: " + decimalinterestrate); 
      System.out.println("Interest:" + decimalInterest); 
      System.out.println(); 

      //see if user wants to continue    
      System.out.print("Continue? (y/n): "); 
      choice = sc.next(); 
      System.out.println(); 


     } 

    } 

    } 

---

import java.util.Scanner; 
    import java.text.NumberFormat; 
    import java.math.*; 

    public class project3a 
    { 


    public static void main(String[] args) 
    { 
     System.out.println("Welcome to the interest calculator"); 
     System.out.println(); 


     // create a scanner object and start while loop    
     Scanner sc = new Scanner(System.in); 
     String choice ="y"; 
     while (choice.equalsIgnoreCase("y")) 
     { 

      //Get input from user 
      System.out.print("Enter Loan amount: "); 
      double Loanamount = sc.nextDouble(); 

      System.out.print("Enter Interest Rate: "); 
      double interestrate = sc.nextDouble(); 

      //calculate results 
      double Interest = Loanamount * interestrate; 

      //format and display results 
      NumberFormat currency = NumberFormat.getCurrencyInstance(); 
      NumberFormat percent = NumberFormat.getPercentInstance(); 
      String message = 
       "Loan amount: " + currency.format (Loanamount) + "\n" 
       + "Interest rate: " + percent.format (interestrate)+ "\n" 
       + "Interest:  " + currency.format (Interest) + "\n"; 

      System.out.println(message); 

      //see if user wants to continue    
      System.out.print("Continue? (y/n): "); 
      choice = sc.next(); 
      System.out.println(); 


     } 

    } 

    } 

Answer 1

BigDecimal有方法doubleValue()，你可以在NumberFormat使用。

BigDecimal bd = new BigDecimal("15.25"); 
NumberFormat currency = NumberFormat.getCurrencyInstance(); 
NumberFormat percent = NumberFormat.getPercentInstance(); 

System.out.println(currency.format(bd.doubleValue())); //In Brazil outputs R$ 15,25 
System.out.println(percent.format(bd.doubleValue())); // 1.525%