Java编译报".class" expected错误是什么原因？附完整出错代码

算力阿峰

2026-9-28

编译错误原因及修复方案

核心错误点

方法调用语法不符合规范
Java定义方法时需要标注参数类型，但调用方法时不能加参数类型声明，你写的presentValue(double f, double r ,int n)属于把方法定义的语法套到了调用环节，是触发所有报错的核心原因。
同时你的presentValue方法内部已经通过弹窗获取了三个参数的数值，根本不需要从外部传参，所以方法定义里的参数也可以直接删掉，避免逻辑冗余。
存在不可达代码
presentValue方法中return p;执行后会直接结束方法返回结果，后面的System.exit(0);永远不会运行，属于无效代码需要删除。

修复后完整代码

import javax.swing.JOptionPane;

/*This program computes a customers present
deposit to make to obtain a desired future
value
*/
public class Deposit
{
  //Main method
  public static void main(String[] args)
  {
    //Calling the present value method
    double results=presentValue();
    //Displaying the present value 
    JOptionPane.showMessageDialog(null, "You have to deposit: $" + results);
  }

  public static double presentValue()
  {
    //Declaring the input variable
    String input;
    double f, r;
    int n;

    //Taking inputs from the customer
    //Future value
    input = JOptionPane.showInputDialog("Enter your desired future value:");
    f = Double.parseDouble(input);

    //Annual Interest Rate
    input = JOptionPane.showInputDialog("Enter the annual interest rate (e.g. 0.05 for 5%):");
    r = Double.parseDouble(input);

    //Number of years
    input = JOptionPane.showInputDialog("Enter the number of years:");
    n = Integer.parseInt(input);

    //Calculating the present value the customer has to deposit
    double p = f / Math.pow((1 + r), n);

    //Returning the value to the present value method
    return p;
  }
}