/*
Chapter 7: Average of grades
Programmer:
Date:
Filename: Averages.java
Purpose: To use the Java Swing interface to calculate the average of up to 50 grades.
Average is calculated once -1 is entered as a value. The grades are then sorted
from lowest to highest and displayed in a content pane which also displayes the average.
*/
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
import java.text.DecimalFormat;
public class Averages extends JFrame
{
//construct conponents
static JLabel title = new JLabel("Average of Grades");
static JTextPane textPane = new JTextPane();
static int numberOfGrades = 0;
static int total = 0;
static DecimalFormat twoDigits = new DecimalFormat ("##0.00");
//set array
static int[] grades = new int[50];
//create content pane
public Container createContentPane()
{
//create JTextPane and center panel
JPanel northPanel = new JPanel();
northPanel.setLayout(new FlowLayout());
northPanel.add(title);
JPanel centerPanel = new JPanel();
textPane = addTextToPane();
JScrollPane scrollPane = new JScrollPane(textPane);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setPreferredSize(new Dimension(500,200));
centerPanel.add(scrollPane);
//create Container and set attributes
Container c = getContentPane();
c.setLayout(new BorderLayout(10,10));
c.add(northPanel,BorderLayout.NORTH);
c.add(centerPanel,BorderLayout.CENTER);
return c;
}
//method to add new text to JTextPane
public static JTextPane addTextToPane()
{
Document doc = textPane.getDocument();
try
{
// clear previous text
doc.remove(0,doc.getLength());
//insert title
doc.insertString(0,"Grades\n",textPane.getStyle("large"));
//insert grades and calculate average
for(int j=0; j<grades.length; j++)
{
doc.insertString(doc.getLength(), grades[j] + "\n", textPane.getStyle("large"));
}
}
catch(BadLocationException ble)
{
System.err.println("Couldn't insert text");
}
return textPane;
}
//method to sort array
public void grades(int grdArray[])
{
//sort int array
for (int pass = 1; pass<grdArray.length; pass++)
{
for (int element = 0; element<grdArray.length -1; element++)
{
swap(grades, element, element + 1);
}
}
addTextToPane();
}
//method to swap elements of array
public void swap(int swapArray[], int first, int second)
{
int hold;
hold = swapArray[first];
swapArray[first] = swapArray[second];
swapArray[second] = hold;
}
//execute method at run time
public static void main(String args[])
{
JFrame.setDefaultLookAndFeelDecorated(true);
Averages f = new Averages();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//accept first grade
int integerInput = Integer.parseInt(JOptionPane.showInputDialog(null, "Please enter a grade (0-100) or -1 to calculate the average"));
//while loop accepts more grades, keeps count, and calulates the total
int count = 0;
int[] grades = new int[50];
int num = 0;
while (count<50 && num!= -1)
{
num = Integer.parseInt(JOptionPane.showInputDialog(null, "Please enter a grade (0-100) or -1 to calculate the average" + (count+1)));
if(num!=-1)
grades[count] = num;
count++;
}
//create content pane
f.setContentPane(f.createContentPane());
f.setSize(600,375);
f.setVisible(true);
}
}
请分解问题。
从统计数据开始:
/**
* Statistics
* @author Michael
* @link http://stackoverflow.com/questions/15626262/averaging-grades-using-java-swing?noredirect=1#comment22167503_15626262
* @since 3/25/13 7:50 PM
*/
public class Statistics {
public static double getAverage(int numValues, int [] values) {
double average = 0.0;
if ((values != null) && (numValues > 0) && (values.length >= numValues)) {
for (int i = 0; i < numValues; ++i) {
average += values[i];
}
average /= numValues;
}
return average;
}
}
接下来,我建议您暂时将 Swing 完全排除在外。制作纯文本输入/输出 UI。
import java.util.Scanner;
/**
* StatisticsDriver
* @author Michael
* @link http://stackoverflow.com/questions/15626262/averaging-grades-using-java-swing?noredirect=1#comment22167503_15626262
* @since 3/25/13 7:50 PM
*/
public class StatisticsDriver {
public static final int MAX_VALUES = 50;
public static void main(String [] args) {
int [] values = new int[MAX_VALUES];
Scanner scanner = new Scanner(System.in);
boolean getAnotherValue;
int numValues = 0;
do {
System.out.print("next value: ");
String input = scanner.nextLine();
if (input != null) {
values[numValues++] = Integer.valueOf(input.trim());
}
System.out.print("another? [y/n]: ");
input = scanner.nextLine();
getAnotherValue = "y".equalsIgnoreCase(input);
} while (getAnotherValue);
System.out.println(Statistics.getAverage(numValues, values));
}
}