Question

我把这个程序放在一起，我的第一个程序，但是在我输入框中的值之后，最后的输出是“0”而不是减法。我不知道我错过了什么。

import java.util.Scanner;
import javax.swing.JOptionPane;
public class PSEUDOCODE_PROGRAM {

public static void main(String[] args) {
   Scanner scnr= new Scanner(System.in);

   String applesHad = " ";
   String applesNeed = " ";
   String orangesHad = " ";
   String orangesNeed = " ";
   int applesTheyHave = 0;
   int applesTheyNeed = 0;
   int orangesTheyHave = 0;
   int orangesTheyNeed = 0;
   int applesToOrder = 0;
   int orangesToOrder = 0;
   applesToOrder = applesTheyNeed - applesTheyHave;
   orangesToOrder = orangesTheyNeed - orangesTheyHave;

//Ask produce buyer how many apples are in stock
applesHad= JOptionPane.showInputDialog(null, "How many apples do you have: ");
applesTheyHave = Integer.parseInt(applesHad);
applesHad= JOptionPane.showInputDialog(null, "How many apples do you need: ");
applesTheyNeed = Integer.parseInt(applesHad);
//Ask produce buyer how many oranges are in stock
orangesHad= JOptionPane.showInputDialog(null, "How many oranges do you have:      ");
orangesTheyHave = Integer.parseInt(orangesHad);
orangesHad= JOptionPane.showInputDialog(null, "How many oranges do you need: ");
orangesTheyNeed = Integer.parseInt(orangesHad);
JOptionPane.showMessageDialog(null, "You must order " + applesToOrder + "         apples and " + orangesToOrder + " oranges!");

Answer 1

非常简单，您在用户输入后不会再次计算applesToOrder和orangesToOrder，因此他们将之前的值0取出，只需将这些行放在上一个{{1}之上声明并看到魔法。

JOptionPane

Answer 2

在用户提供输入值之前，您正在执行mat操作，在JOptionPane部分之后移动它......

applesToOrder = applesTheyNeed - applesTheyHave;
orangesToOrder = orangesTheyNeed - orangesTheyHave;

Answer 3

当你这样做时

applesToOrder = applesTheyNeed - applesTheyHave;
orangesToOrder = orangesTheyNeed - orangesTheyHave;

applesTheyNeed的值，所有其他变量都是0，因此applesToOrder就像这样读取

applesToOrder = applesTheyNeed - applesTheyHave

applesToOrder = 0 - 0

applesToOrder = 0

之后更改了值applesTheyNeed和其他人，不会影响 applesToOrder

的值

要修复此，只需在接受输入后放置语句

减法在java程序中不起作用（缺少某些东西）

3 个答案: