为什么我的代码的最后一行不打印？另外，对于我来说，将数字舍入到2位小数最简单的方法是什么？

Question

运行我的程序时，显示年度天然气费用的最后一行没有显示......我做错了什么？也想一些帮助四舍五入到小数点后两位... 我试图实施一些策略，但没有一个工作。 任何帮助表示赞赏！

public class GasExpenses { 
public static void main(String[] args) { 

//Use scanner in order to retrieve user input. 
Scanner keyboard= new Scanner(System.in); 

//Declare variables. 
int milesPerWeek; 
double milesPerGallon,costOfGas; 


System.out.println("GAS EXPENSES"); 
//Get user input. 
System.out.println("How many miles do you drive a week?"); 
milesPerWeek = keyboard.nextInt(); 

//Get user input. 
System.out.println("How many miles per gallon does your auto get?"); 
milesPerGallon=keyboard.nextDouble(); 

//Get user input. 
System.out.println("What is the current cost of gas?"); 
costOfGas=keyboard.nextDouble(); 

//Calculate miles per year. 
int milesPerYear=(milesPerWeek*52); 
//Display calculated yearly mileage. 
System.out.println("At " + milesPerWeek + "miles per week, you travel "+ 
milesPerYear + " miles per year."); 

//Calculate and display calculated weekly & yearly gallons of gas used. 
double gallonsPerWeek=(milesPerWeek/milesPerGallon); 
System.out.println("Gallons per week:" + gallonsPerWeek); 
double gallonsPerYear=(gallonsPerWeek*52); 
System.out.println("Gallons per year:" + gallonsPerYear); 

//Calculate and display calculated weekly & yearly gas expense. 
System.out.println("With gas at $" +costOfGas + " per gallon, you will 
spend: "); 
double weeklyGasExpense=(costOfGas*milesPerWeek); 
System.out.println("Gas expense per week: $" +weeklyGasExpense); 
double yearlyGasExpense=(costOfGas*milesPerYear); 
System.out.println("Gas expense per year: $" +yearlyGasExpense); 

//Calculate and display calculated weekly & yearly gas expense based on 
increased gas price. 
double costIncrease= (costOfGas+1); 
System.out.println("If gas goes up by one dollar per gallon to $" + 
costIncrease +(" per gallon, you will spend:")); 
double weeklyIncreasedGas=(costIncrease*milesPerWeek); 
double yearlyIncreasedGas=(costIncrease*milesPerYear); 
System.out.println("Gas expense per week : $" +weeklyIncreasedGas); 
System.out.print("Gas expense per year : $" +yearlyIncreasedGas); 
}} 

Answer 1

在代码末尾运行system.out.flush（）以确保打印出所有内容。

取整，你可以试试这个答案round up to 2 decimal places in java?

Answer 2

对于第一个问题，此行对我的作品给你的代码：

System.out.print("Gas expense per year : $" +yearlyIncreasedGas); 

对于第二个做到这一点：

double number = 111.12345; 
double result = Math.round(number * 100.0)/100.0;