java有人知道为什么这些if-else语句不起作用吗？

Question

public class Salary
{
    public static void main (String[] args)
    {
        double currentSalary; // employee's current salary
        double raise; // amount of the raise
        double percentRaise;   // percentage of the raise
        double newSalary; // new salary for the employee
        String rating; // performance rating

        Scanner scan = new Scanner(System.in);

        System.out.print ("Enter the current salary: ");
        currentSalary = scan.nextDouble();

        System.out.print ("Enter the performance rating (Excellent, Good, or Poor): ");
        rating = scan.next();
        if (rating.equals("Excellent"))

            percentRaise = .06;   
            raise = (.06 * currentSalary);


            else if (rating.equals("Good"))

                    percentRaise = .04;
                   raise = (.04 * currentSalary); 


                   else  if (rating.equals("Poor"))

                       percentRaise = .015;
                       raise = (.015 * currentSalary);

        //Compute the raise using if ...

        newSalary = currentSalary + raise;

        //Print the results
        NumberFormat money = NumberFormat.getCurrencyInstance();
        System.out.println();
        System.out.println("Current Salary: " + money.format(currentSalary));
        System.out.println("Amount of your raise: " + money.format(raise));
        System.out.println( "Your new salary: " + money. format (newSalary) );
        System.out.println();
        scan.close();
    }
}

如果我在空白处加上{和}，则表示raise未初始化。不管我做什么，我似乎都想不出办法让它运转起来。现在，它告诉我删除else让它运行，但如果我这样做，无论我写得好、好或差。它的薪水是0.015*所以我不能跑得很好

Answer 1

您需要将if语句包装到这些内容中-->；“{}”

所以它是这样的：

if(statement){
   //then do someting
}else{
   //then do something else
}

Answer 2

如果只包含一个命令，则只能编写不带大括号的if语句；如果有多个命令（多行），则需要将这些命令括在大括号中

Answer 3

if (rating.equals("Excellent"))
    percentRaise = .06;   
    raise = (.06 * currentSalary);
else if (rating.equals("Good"))

无法编译，因为Java将其视为

if (rating.equals("Excellent"))
    percentRaise = .06;   

raise = (.06 * currentSalary);

else if (rating.equals("Good"))

这意味着编译器将抱怨没有if语句的else-if

您遇到的另一个问题（当您在语句周围放置{ }）是因为Java无法确定局部变量的初始值

这意味着Java根本不知道如何处理newSalary = currentSalary + raise;，因为无法保证raise将有一个赋值给它

您可以通过在if-else块的末尾添加一个else条件，或者简单地为局部变量提供一个初始值来克服这个问题

    double currentSalary = 0; // employee's current salary
    double raise = 0; // amount of the raise
    double percentRaise = 0;   // percentage of the raise
    double newSalary = 0; // new salary for the employee
    String rating = ""; // performance rating

虽然这可能看起来很烦人，但最好是获得一些完全随机的值，您必须花时间尝试调试；）

已更新

记住，String#equals区分大小写，这意味着“优秀”不等于“优秀”

您可以使用String#equalsIgnoreCase

Answer 4

您必须确保，如果if语句包含多行代码，那么它将用大括号包装

public class Salary
 {
public static void main (String[] args)
{
    double currentSalary; // employee's current salary
    double raise; // amount of the raise
    double percentRaise;   // percentage of the raise
    double newSalary; // new salary for the employee
    String rating; // performance rating

    Scanner scan = new Scanner(System.in);

    System.out.print ("Enter the current salary: ");
    currentSalary = scan.nextDouble();

    System.out.print ("Enter the performance rating (Excellent, Good, or Poor): ");
    rating = scan.next();
    if (rating.equals("Excellent"))
         {
        percentRaise = .06;   
        raise = (.06 * currentSalary);

         }
        else if (rating.equals("Good"))
        {
                percentRaise = .04;
               raise = (.04 * currentSalary); 

          }
               else  if (rating.equals("Poor"))
       {
                   percentRaise = .015;
                   raise = (.015 * currentSalary);
          }
    //Compute the raise using if ...

    newSalary = currentSalary + raise;

    //Print the results
    NumberFormat money = NumberFormat.getCurrencyInstance();
    System.out.println();
    System.out.println("Current Salary: " + money.format(currentSalary));
    System.out.println("Amount of your raise: " + money.format(raise));
    System.out.println( "Your new salary: " + money. format (newSalary) );
    System.out.println();
    scan.close();
}

}