寻找最高的10

Question

我要说实话，我一直在做一个任务，我比BEYOND卡住了。我正在创建一个简单的Java applet，可以让用户输入10个数字。该程序清理输入，确保只输入一个数字，并且该数字必须介于0和9之间。

至今没有问题。使用给定的例子，在网络上搜索正确的语法和逻辑。我的代码编译没有抱怨。然而，一旦我尝试了我的第一个号码，只要它的有效输入，我的程序刚起来，并告诉我刚输入的号码是最大的，并且不等待输入10个号码。

我的猜测是我有一半的applet程序，并且我没有输出正确的，或者我的循环中有什么错误，但逻辑看起来不错。

差点忘了提。我不知道如何在applet中输出文本，任何帮助都很棒，但它不是我最关心的问题。

我当前的代码：

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

按照预期，您正在循环10次，但每次只需要getText()即可获得该字段的值。这不会等待用户更改号码，因此所有10个号码都是相同的。您必须将counter和largest定义为字段，并且每次调用actionPerformed时都会更改。这里的代码：

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

这是因为该行

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

是只要您已在该领域的一些做10次，你在循环结束之前，没有时间去改变字段中的数字。