尋找最高的10

Question

我要說實話，我一直在做一個任務，我比BEYOND卡住了。我正在創建一個簡單的Java applet，可以讓用戶輸入10個數字。該程序清理輸入，確保只輸入一個數字，並且該數字必須介於0和9之間。

至今沒有問題。使用給定的例子，在網絡上搜索正確的語法和邏輯。我的代碼編譯沒有抱怨。然而，一旦我嘗試了我的第一個號碼，只要它的有效輸入，我的程序剛起來，並告訴我剛輸入的號碼是最大的，並且不等待輸入10個號碼。

我的猜測是我有一半的applet程序，並且我沒有輸出正確的，或者我的循環中有什麼錯誤，但邏輯看起來不錯。

差點忘了提。我不知道如何在applet中輸出文本，任何幫助都很棒，但它不是我最關心的問題。

我當前的代碼：

import java.awt.*; 
import java.applet.*; 
import java.awt.event.*; 
import javax.swing.JOptionPane; 

public class largest extends Applet implements ActionListener{ 
private static final long serialVersionUID = 1L; 


//Create components for Applet 
Label numberLabel = new Label("Enter a number:"); 
TextField numberField = new TextField(10); // Sets the size of the text field, You still may type as much data into the field that you want, input will need to be sanitized later 

Label topNumberLabel = new Label("The top number is:"); 
Button calcButton = new Button("Ok"); 
public void init() 
{ 
    // Add controls to the applet window 
    add(numberLabel); 
    add(numberField); 
    add(topNumberLabel); 
    add(calcButton); 
    calcButton.addActionListener(this); 
    setSize(300, 200); // Sets the size of the applet window 
} 

public void actionPerformed(ActionEvent e) { 
    // Variables for counting, user input, and storage for largest number 
    double counter = 0; 
    double number = 0; 
    double largest = 0; 

    // Allows user to input 10 times 
    while (counter<10) 
    { 
     try { //Sanitize user input, make sure input entered is a number 
      number = Double.parseDouble(numberField.getText()); 
     } catch (NumberFormatException ex) { 
      numberField.requestFocus(); 
      JOptionPane.showMessageDialog(null, "Input invalid, please enter an integer", 
        "///-D-A-T-A---E-R-R-O-R-\\\\\\", JOptionPane.ERROR_MESSAGE); 
      return; 
     } 
     if (number < 0 || number > 9) { //Sanitize user input, make sure the given number is between 0 and 9 
      numberField.requestFocus(); 
      JOptionPane.showMessageDialog(null, 
        "The number entered must be between 0 and 9", 
        "///-D-A-T-A---E-R-R-O-R-\\\\\\", JOptionPane.ERROR_MESSAGE); 
      return; 
     } 
     counter++; 

    // Determine what the largest number entered is by comparing to a baseline 
    // of previous numbers or zero if just beginning loop 
    if (number > largest)largest=number; 

    } 

     // Display's the largest number that got entered by user 
     JOptionPane.showMessageDialog(null," The largest number entered was " + largest); 
    } 

}

Answer 1

按照預期，您正在循環10次，但每次只需要getText()即可獲得該字段的值。這不會等待用戶更改號碼，因此所有10個號碼都是相同的。您必須將counter和largest定義爲字段，並且每次調用actionPerformed時都會更改。這裏的代碼：

import java.awt.*; 
import java.applet.*; 
import java.awt.event.*; 
import javax.swing.JOptionPane; 

public class largest extends Applet implements ActionListener{ 
    private static final long serialVersionUID = 1L; 

    private int counter = 0; // These are the variables 
    private double largest = 0; // from actionPerformed(). 

    // ... 

    public void actionPerformed(ActionEvent e) { 
     // Variable for user input 
     double number = 0; 

     try { //Sanitize user input, make sure input entered is a number 
      number = Double.parseDouble(numberField.getText()); 
     } catch (NumberFormatException ex) { 
      numberField.requestFocus(); 
      JOptionPane.showMessageDialog(null, 
        "Input invalid, please enter an integer", 
        "///-D-A-T-A---E-R-R-O-R-\\\\\\", 
        JOptionPane.ERROR_MESSAGE); 
      return; 
     } 
     if (number < 0 || number > 9) { //Sanitize user input, make sure the given number is between 0 and 9 
      numberField.requestFocus(); 
      JOptionPane.showMessageDialog(null, 
        "The number entered must be between 0 and 9", 
        "///-D-A-T-A---E-R-R-O-R-\\\\\\", 
        JOptionPane.ERROR_MESSAGE); 
      return; 
     } 
     counter++; 
     // Determine what the largest number entered is by comparing to a baseline 
     // of previous numbers or zero if just beginning loop 
     if (number > largest)largest=number; 
     // Allows user to input 10 times 
     if (counter==10) 
     { 
      // Display's the largest number that got entered by user 
      JOptionPane.showMessageDialog(null, 
        "The largest number entered was " + largest); 
     } 
    } 
} 

Answer 2

這是因爲該行

number = Double.parseDouble(numberField.getText()); 

是隻要您已在該領域的一些做10次，你在循環結束之前，沒有時間去改變字段中的數字。