【发布时间】：2014-01-22 04:21:52
【问题描述】：
好的，所以我最近询问了如何在 java 中访问数组的各个列，我得到了一个完美的答案。然后，我打算计算诸如此列中的最大值和平均值之类的东西。但是，我遇到了一个问题。为了访问每个值，我假设该列也需要被视为一个数组。但是，我访问每一列的方式是将其存储为双精度列。因此，我不知道如何取每一列并计算东西。任何人都可以帮助我吗？很抱歉在这里发布了这么多看起来似乎没什么的东西，但是我们已经有 12 周没有老师了，预计只能通过自学来完成这项工作，我真的被困住了。
import java.awt.EventQueue;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.JTextField;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.JButton;
import java.awt.TextArea;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;//Importing any required tools.
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
public class CSVFiles extends JFrame { //Class, inherits properties of the JFrame.
private JPanel contentPane; //Create a container for the GUI.
//Create other components used in the GUI
private JTextField maxTxtVCC;
private JTextField maxTxtTemp;
private JTextField maxTxtLight;
private JTextField minTxtLight;
private JTextField avTxtLight;
private JTextField minTxtTemp;
private JTextField avTxtTemp;
private JTextField minTxtVCC;
private JTextField avTxtVCC;
private JButton btnMax;
private JButton btnMin;
private JButton btnAv;
private JTextField opnTxt;
private JButton btnOpn;
private TextArea textArea;
private JFileChooser fc;
private String content = "";
String [] contentCSV = new String [53000]; //String array to hold the data, 2000 gives more than enough space
int totalValues; //Used to hold the amount of values in the array (52790 ish)
Double[][] values;
double c4, c5, c6;
/**
* Launch the application.
*/
public static void main(String[] args) { //Main method
EventQueue.invokeLater(new Runnable() {
public void run() { //Create a runnable method
try {
CSVFiles frame = new CSVFiles(); //Launch the GUI
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace(); //Print errors
}
}
});
}
/**
* Create the frame.
*/
public CSVFiles() { //Open constructor
super ("CSV Files"); //Create a title for the GUI
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Instruct how the GUI is closed
setBounds(100, 100, 800, 600); //Set size and location
contentPane = new JPanel(); //Declare the JPanel
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5)); //Create a boarder
setContentPane(contentPane); //Add the JPanel
contentPane.setLayout(null); //Set the layout
maxTxtVCC = new JTextField(); //Declare this text field
maxTxtVCC.setBounds(113, 534, 86, 20); //Set size and location
maxTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtVCC); //Add to the content pane
maxTxtTemp = new JTextField(); //Declare this text field
maxTxtTemp.setBounds(113, 503, 86, 20); //Set size and location
maxTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtTemp); //Add to the content pane
maxTxtLight = new JTextField(); //Declare this text field
maxTxtLight.setBounds(113, 472, 86, 20); //Set size and location
maxTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtLight); //Add to the content pane
JLabel lblLight = new JLabel("Light"); //Declare this label
lblLight.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblLight.setBounds(22, 469, 46, 17); //Set size and location
contentPane.add(lblLight); //Add to the content pane
JLabel lblTemp = new JLabel("Temperature"); //Declare this label
lblTemp.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblTemp.setBounds(10, 503, 109, 17); //Set size and location
contentPane.add(lblTemp);
JLabel lblVCC = new JLabel("VCC"); //Declare this label
lblVCC.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblVCC.setBounds(22, 534, 46, 17); //Set size and location
contentPane.add(lblVCC); //Add to the content pane
minTxtLight = new JTextField(); //Declare this text field
minTxtLight.setBounds(221, 472, 86, 20); //Set size and location
minTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtLight); //Add to the content pane
avTxtLight = new JTextField(); //Declare this text field
avTxtLight.setBounds(331, 472, 86, 20); //Set size and location
avTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtLight); //Add to the content pane
minTxtTemp = new JTextField(); //Declare this text field
minTxtTemp.setBounds(221, 503, 86, 20); //Set size and location
minTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtTemp); //Add to the content pane
avTxtTemp = new JTextField(); //Declare this text field
avTxtTemp.setBounds(331, 503, 86, 20); //Set size and location
avTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtTemp); //Add to the content pane
minTxtVCC = new JTextField(); //Declare this text field
minTxtVCC.setBounds(221, 534, 86, 20); //Set size and location
minTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtVCC); //Add to the content pane
avTxtVCC = new JTextField(); //Declare this text field
avTxtVCC.setBounds(331, 534, 86, 20); //Set size and location
avTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtVCC); //Add to the content pane
btnMax = new JButton("Maximum"); //Declare this button
btnMax.setBounds(110, 438, 89, 23); //Set size and location
contentPane.add(btnMax); //Add to the content pane
btnMin = new JButton("Minimum"); //Declare this button
btnMin.setBounds(221, 438, 89, 23); //Set size and location
contentPane.add(btnMin); //Add to the content pane
btnAv = new JButton("Average"); //Declare this button
btnAv.setBounds(328, 438, 89, 23); //Set size and location
contentPane.add(btnAv); //Add to the content pane
textArea = new TextArea(); //Declare this text area
textArea.setBounds(22, 55, 551, 367); //Set size and location
textArea.setEditable(false); //Set it so it cannot be edited
contentPane.add(textArea); //Add to the content pane
btnOpn = new JButton("Open File"); //Declare this button
btnOpn.addActionListener(new ActionListener() { //Add an action listener to this button
public void actionPerformed(ActionEvent arg0) { //Method for action performed
try{
fc = new JFileChooser(); //Declare the file chooser
fc.setFileFilter(new FileNameExtensionFilter("CSV Files", "csv")); //Add a filter for only choosing CSV files
fc.removeChoosableFileFilter(fc.getAcceptAllFileFilter()); //Remove option to select any file type
int returnVal = fc.showOpenDialog(contentPane); // Open the file chooser
File f; //Create a file to hold the data
//If the selected file is approved by the file chooser...
if(returnVal == JFileChooser.APPROVE_OPTION){
f = fc.getSelectedFile(); //Stored selected file into file variable
BufferedReader in = new BufferedReader(new FileReader(f));
StringBuilder builder = new StringBuilder();
String line = "";
textArea.append("Opening "+ f.getAbsolutePath()); //Print out file path
textArea.append("\nLoading file...\n\n"); //Print out loading message and some new lines
in.readLine(); //Skip the first line as it's just headers
int index = 0; //Integer used to label the indexes of the array
while((line = in.readLine()) != null){
builder.append(line);
builder.append("\n");
index++; //increment the index to move the next one up for the next line
String temp[] = line.split(",");
c4 = Double.parseDouble(temp[3]);
c5 = Double.parseDouble(temp[4]);
c6 = Double.parseDouble(temp[5]);
}
totalValues = index; //Set a value to the total values
textArea.append(builder.toString()); //Using the string builder to compile the text
textArea.append("\n*** End of File"); //Print the file onto the text area and an end of file message
in.close(); //Close the reader.
values = new Double [index][3];
}
else{
f = null;
}
}
catch(Exception e){
e.printStackTrace();
}
}
});
btnOpn.setBounds(484, 26, 89, 23); //Set size and location
contentPane.add(btnOpn); //Add to the content pane
opnTxt = new JTextField(); //Declare this text field
opnTxt.setBounds(22, 27, 452, 20); //Set size and location
opnTxt.setEditable(false); //Set it so it cannot be edited
contentPane.add(opnTxt); //Add to the content pane
}
//Methods for Calculations
public static double findMax(double[] array){
double max;
max = array[0];
for(int i=1;i<array.length;++i){
if(array[i]>max){
max = array[i];
}
}
return max;
}
}
此外，在此之后，我尝试了一个替代代码，在该代码中，我不是获取单个列，而是将不需要的列存储到一个数组中，以便在计算过程中将它们无效，但这也不起作用。我承认我并没有完全理解这种方法，但它是基于一个示例代码提供给我们的，没有任何解释它在做什么，所以我想我至少会尝试一下。它在文本区域显示文件，但当我尝试单击最大按钮时会出现空指针异常。 http://gyazo.com/27ef7cf9f4bc0c72ecdc3c1f84e6d0f8 再次感谢任何帮助。我有点赶时间，因为去年我的班级来找我帮忙，因为我在空闲时间看了一系列关于 Java 基础的系列，所以我们第一年的工作没有问题，他们来找我寻求帮助.但是，我没有找到 java 系列或类似的东西，就像特定的视频一样，只有一点帮助。所以，是的，非常感谢您的帮助。 :)
import java.awt.EventQueue;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.JTextField;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.JButton;
import java.awt.TextArea;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;//Importing any required tools.
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
public class CSVFiles extends JFrame { //Class, inherits properties of the JFrame.
private JPanel contentPane; //Create a container for the GUI.
//Create other components used in the GUI
private JTextField maxTxtVCC;
private JTextField maxTxtTemp;
private JTextField maxTxtLight;
private JTextField minTxtLight;
private JTextField avTxtLight;
private JTextField minTxtTemp;
private JTextField avTxtTemp;
private JTextField minTxtVCC;
private JTextField avTxtVCC;
private JButton btnMax;
private JButton btnMin;
private JButton btnAv;
private JTextField opnTxt;
private JButton btnOpn;
private TextArea textArea;
private JFileChooser fc;
private String content = "";
String [] contentCSV = new String [53000]; //String array to hold the data, 2000 gives more than enough space
int totalValues; //Used to hold the amount of values in the array (52790 ish)
Double[][] values;
/**
* Launch the application.
*/
public static void main(String[] args) { //Main method
EventQueue.invokeLater(new Runnable() {
public void run() { //Create a runnable method
try {
CSVFiles frame = new CSVFiles(); //Launch the GUI
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace(); //Print errors
}
}
});
}
/**
* Create the frame.
*/
public CSVFiles() { //Open constructor
super ("CSV Files"); //Create a title for the GUI
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Instruct how the GUI is closed
setBounds(100, 100, 800, 600); //Set size and location
contentPane = new JPanel(); //Declare the JPanel
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5)); //Create a boarder
setContentPane(contentPane); //Add the JPanel
contentPane.setLayout(null); //Set the layout
maxTxtVCC = new JTextField(); //Declare this text field
maxTxtVCC.setBounds(113, 534, 86, 20); //Set size and location
maxTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtVCC); //Add to the content pane
maxTxtTemp = new JTextField(); //Declare this text field
maxTxtTemp.setBounds(113, 503, 86, 20); //Set size and location
maxTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtTemp); //Add to the content pane
maxTxtLight = new JTextField(); //Declare this text field
maxTxtLight.setBounds(113, 472, 86, 20); //Set size and location
maxTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtLight); //Add to the content pane
JLabel lblLight = new JLabel("Light"); //Declare this label
lblLight.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblLight.setBounds(22, 469, 46, 17); //Set size and location
contentPane.add(lblLight); //Add to the content pane
JLabel lblTemp = new JLabel("Temperature"); //Declare this label
lblTemp.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblTemp.setBounds(10, 503, 109, 17); //Set size and location
contentPane.add(lblTemp);
JLabel lblVCC = new JLabel("VCC"); //Declare this label
lblVCC.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblVCC.setBounds(22, 534, 46, 17); //Set size and location
contentPane.add(lblVCC); //Add to the content pane
minTxtLight = new JTextField(); //Declare this text field
minTxtLight.setBounds(221, 472, 86, 20); //Set size and location
minTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtLight); //Add to the content pane
avTxtLight = new JTextField(); //Declare this text field
avTxtLight.setBounds(331, 472, 86, 20); //Set size and location
avTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtLight); //Add to the content pane
minTxtTemp = new JTextField(); //Declare this text field
minTxtTemp.setBounds(221, 503, 86, 20); //Set size and location
minTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtTemp); //Add to the content pane
avTxtTemp = new JTextField(); //Declare this text field
avTxtTemp.setBounds(331, 503, 86, 20); //Set size and location
avTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtTemp); //Add to the content pane
minTxtVCC = new JTextField(); //Declare this text field
minTxtVCC.setBounds(221, 534, 86, 20); //Set size and location
minTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtVCC); //Add to the content pane
avTxtVCC = new JTextField(); //Declare this text field
avTxtVCC.setBounds(331, 534, 86, 20); //Set size and location
avTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtVCC); //Add to the content pane
btnMax = new JButton("Maximum"); //Declare this button
btnMax.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
double tempArray1 [] = new double [totalValues];
double tempArray2 [] = new double [totalValues];
double tempArray3 [] = new double [totalValues];
for (int i = 0; i < totalValues; i++){
tempArray1[i] = values[i][0]; //assign the indexes along side each individual sensor from sensor value
tempArray2[i] = values[i][1];
tempArray3[i] = values[i][2];
}
//execute the method defined in Utils.java to calculate maximum
maxTxtLight.setText(findMax(tempArray1)+"");
maxTxtTemp.setText(findMax(tempArray2)+"");
maxTxtVCC.setText(findMax(tempArray3)+"");
}
});
btnMax.setBounds(110, 438, 89, 23); //Set size and location
contentPane.add(btnMax); //Add to the content pane
btnMin = new JButton("Minimum"); //Declare this button
btnMin.setBounds(221, 438, 89, 23); //Set size and location
contentPane.add(btnMin); //Add to the content pane
btnAv = new JButton("Average"); //Declare this button
btnAv.setBounds(328, 438, 89, 23); //Set size and location
contentPane.add(btnAv); //Add to the content pane
textArea = new TextArea(); //Declare this text area
textArea.setBounds(22, 55, 551, 367); //Set size and location
textArea.setEditable(false); //Set it so it cannot be edited
contentPane.add(textArea); //Add to the content pane
btnOpn = new JButton("Open File"); //Declare this button
btnOpn.addActionListener(new ActionListener() { //Add an action listener to this button
public void actionPerformed(ActionEvent arg0) { //Method for action performed
try{
fc = new JFileChooser(); //Declare the file chooser
fc.setFileFilter(new FileNameExtensionFilter("CSV Files", "csv")); //Add a filter for only choosing CSV files
fc.removeChoosableFileFilter(fc.getAcceptAllFileFilter()); //Remove option to select any file type
int returnVal = fc.showOpenDialog(contentPane); // Open the file chooser
File f; //Create a file to hold the data
//If the selected file is approved by the file chooser...
if(returnVal == JFileChooser.APPROVE_OPTION){
f = fc.getSelectedFile(); //Stored selected file into file variable
BufferedReader in = new BufferedReader(new FileReader(f));
StringBuilder builder = new StringBuilder();
String line = "";
textArea.append("Opening "+ f.getAbsolutePath()); //Print out file path
textArea.append("\nLoading file...\n\n"); //Print out loading message and some new lines
in.readLine(); //Skip the first line as it's just headers
int index = 0; //Integer used to label the indexes of the array
while((line = in.readLine()) != null){
builder.append(line);
builder.append("\n");
index++; //increment the index to move the next one up for the next line
}
totalValues = index; //Set a value to the total values
textArea.append(builder.toString()); //Using the string builder to compile the text
textArea.append("\n*** End of File"); //Print the file onto the text area and an end of file message
in.close(); //Close the reader.
values = new Double [index][3];
for(int i = 0; i < totalValues; i++){
String cols[] = contentCSV[i].split(",");
String tempMillis = cols[0]; //Use a string to take the millis stamp out of the array
String tempStamp = cols[1]; //Use a string to take the time stamp out of the array
String tempDateTime = cols[2]; //Use a string to take the date stamp out of the array
for(int columns=3;columns<cols.length;++columns){
//temp sensor value holds the 9 sensors and the index numbers, parsing the data into double
values[i][columns-3] = Double.parseDouble(cols[columns]);
}
}
}
else{
f = null;
}
}
catch(Exception e){
e.printStackTrace();
}
}
});
btnOpn.setBounds(484, 26, 89, 23); //Set size and location
contentPane.add(btnOpn); //Add to the content pane
opnTxt = new JTextField(); //Declare this text field
opnTxt.setBounds(22, 27, 452, 20); //Set size and location
opnTxt.setEditable(false); //Set it so it cannot be edited
contentPane.add(opnTxt); //Add to the content pane
}
//Methods for Calculations
public static double findMax(double[] array){
double max;
max = array[0];
for(int i=1;i<array.length;++i){
if(array[i]>max){
max = array[i];
}
}
return max;
}
}
【问题讨论】：
-
要获得更好的答案，请阅读：sscce.org 这里有很多不相关的代码..
-
你没有告诉我们你尝试了什么。我觉得您在不了解 Java 基础知识的情况下从一个问题转到下一个问题。
-
好吧，我使用答案将字符串数组中的数据解析为双精度值，然后保存各个列，但是当我尝试将各个列拆分为一个数组时，它不能；t cuz狭缝方法适用于字符串值。所以我不知道如何取列 c4，它是数组中列中数字的 double 值，然后分别处理其中的每个值进行计算。
-
如果您将代码滚动到正确的位置，则块模式会产生波动。或者，如果你转过头，建筑物。