Java运行速度变慢

Question

我正在尝试执行我的java代码，但它显示时间太长。有一个弹出的方法，说要检查我是否有一个无限循环。我不知道。至少，我不认为我知道。我是java新手，所以我真的需要帮助。我的赋值需要一个for循环，这是我想出来的代码

import java.lang.Math;
public class Main{
  double initialBalance;
  double interestRate;
  double years;
  double totalPayment;
  double firstInterest;
  double lastInterest;
  double totalInterest;
  double totalPrincipal;
  double firstPrincipal;
  double lastPrincipal;
  double firstBalance;
  double lastBalance;
  double monthlyPayment;

  public static final double periodsPerYear = 12;
  public static final double invalidNum = -1.0;

  public Main(double balance, double interest, double Life){
    initialBalance = balance;
    interestRate = interest;
    years = Life;

    //monthlyPayment calculation
    monthlyPayment = initialBalance * ((interestRate/periodsPerYear)+((interestRate/periodsPerYear)/(Math.pow(1+(interestRate/periodsPerYear),periodsPerYear*years)-1)));

    for (double i=0;i<periodsPerYear*years;i++){
      interest = (interestRate/periodsPerYear) * initialBalance;
      totalInterest += interest;

      double principal = monthlyPayment - interest;
      totalPrincipal += principal;

      initialBalance = initialBalance - principal;


      //if statement
      if(i==0){
        firstInterest = interest;
        firstPrincipal = principal;
        firstBalance = initialBalance;
        }
      if(i== (12*2)-1){
        lastInterest = interest;
        lastPrincipal = principal;
        lastBalance = initialBalance;
        }
    }
    totalPayment = totalPrincipal + totalInterest;
  }

  double getMonthlyPayment(){
    return monthlyPayment;
  }

  double getAmount(String month, String type){
    if (month.equals("first")&&type.equals("balance")){
      valid = firstBalance;
    }
    else if (month.equals("first")&&type.equals("interest")){
      valid = firstInterest;
    }
    else if (month.equals("first")&&type.equals("principal")){
      valid = firstPrincipal;
    }
    else if (month.equals("last")&&type.equals("balance")){
      valid = lastBalance0;
    }
    else if (month.equals("last")&&type.equals("interest")){
      valid = lastInterest;
    }
    else if (month.equals("last")&&type.equals("principal")){
      valid = lastPrincipal;
    }
    else{
      valid = invalidNum;
    }
    return Math.round((valid *100.00)/100.00);
  }

  double getTotalInterest(){
    return totalInterest;
  }

  double getTotalPayments(){
    return totalPayment;
  }


  public static void main(String[] args){
        double initialBalance = 10_000.0;
    double interestRate = 0.05;
    double years = 2;

    Main loan = new Main( initialBalance, interestRate, years );
    System.out.println( loan.getMonthlyPayment() );
    System.out.println( loan.getTotalInterest() );
    System.out.println( loan.getTotalPayments() );
    System.out.println( loan.getAmount( "first", "interest" ) );
    System.out.println( loan.getAmount( "first", "principal" ) );
    System.out.println( loan.getAmount( "first", "balance" ) );
    System.out.println( loan.getAmount( "first", "!@#$%^&*()" ) );
    System.out.println( loan.getAmount( "last", "interest" ) );
    System.out.println( loan.getAmount( "last", "principal" ) );
    System.out.println( loan.getAmount( "last", "balance" ) );
    System.out.println( loan.getAmount( "last", "{}|:<>?" ) );
    System.out.println( loan.getAmount( "{)*(&EPQWR", "interest") );
  }
}

我该怎么做才能让它执行得更快呢？我做错了什么？

Answer 1

首先，您提供的代码不能编译。getAmount()中的变量'valid‘和'lastBalance0’未声明。可能你忘了在这个方法的顶部声明'double valid‘，而只键入了'lastBalance0’而不是'lastBalance‘。

您的代码还存在一些其他问题：

• 将for循环中变量'i‘的类型更改为'int’
• 更改返回Math.round((valid *100.00)/100.00)以使用“first”.equals(月度)而不是month.equals("first")返回月度，因为如果month为null，则不会抛出NullPointerException。

Answer 2

正如Alex所指出的，您的代码不能编译。

在修复了这两件事之后，它确实运行了：

• 声明变量double
• 修复拼写错误lastBalance0 to lastBalance

代码运行后，输出如下：

Mon Feb 24 09:34:37 CET 2020
1582533277204
4387.13897340686
5291.335361764231
105291.33536176465
417.0
3970.0
96030.0
-1.0
18.0
4369.0
0.0
-1.0
-1.0
Mon Feb 24 09:34:37 CET 2020
1582533277206

我在开始和结束时在millis中添加了当前日期和时间的打印，程序花了2毫秒执行。