我将如何从 Array 切换到 ArrayList? [英] How would I switch from an Array to an ArrayList?
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问题描述
我现在将所有数据保存到一个数组中.我如何将其切换为保存在对象的 ArrayList 中?我编写了一个基本的学生对象类，但需要帮助将其转换为保存在 Arraylist 中.非常感谢所有帮助.arraylist 在第 28 行创建，数据在第 300 行设置.问题是如何修改代码以存储在 ArrayList 中
I have all the data saving to an array right now. How would I switch it to saving in a ArrayList of objects instead? I have a basic student object class written but need help switching it over to saving in an Arraylist. All help is greatly appreciated. The arraylist is created on line 28 and the data is set at line 300. The question is how to modify code to store in an ArrayList instead
public class IAdvise extends JFrame {
DateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");
String[] columnNames = {"ID", "Name", "Major", "GPA", "Campus", "Home Address", "Phone Number", "Email", "Current CST courses", "Past CST course", "Fusture CST courses", "Notes"};
Object[][] data = new Object[60][12];
ArrayList<Student> al = new ArrayList<Student>();
JTable table = new JTable(data, columnNames) {
@Override
public boolean isCellEditable(int row, int column) {
return false;
}
};
JFrame frame, frame1;
JPanel buttonPanel, buttonPanel2, tablePanel, addPanel, editPanel;
JLabel labelID, labelName, labelMajor, labelGPA, labelCampus, labelAddress, labelPhone, labelEmail,labelCurrent, labelPast, labelFuture, labelNotes;
JTextField txtID, txtName, txtMajor, txtGPA, txtCampus, txtAddress, txtPhone, txtEmail, txtCurrent, txtPast, txtFuture, txtNotes;
JButton btnAdd, btnEdit, btnDelete, btnSort, btnSave, btnAddInput, btnCancel;
int keyCode, rowIndex, rowNumber, noOfStudents;
IAdvise.ButtonHandler bh = new IAdvise.ButtonHandler();
public IAdvise() {
table.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
table.getSelectionModel().addListSelectionListener(new IAdvise.RowListener());
table.getColumnModel().getColumn(1).setPreferredWidth(150);
table.getColumnModel().getColumn(2).setPreferredWidth(150);
table.getColumnModel().getColumn(3).setPreferredWidth(50);
table.getColumnModel().getColumn(4).setPreferredWidth(200);
table.getColumnModel().getColumn(5).setPreferredWidth(250);
table.getColumnModel().getColumn(6).setPreferredWidth(150);
table.getColumnModel().getColumn(7).setPreferredWidth(150);
table.getColumnModel().getColumn(8).setPreferredWidth(150);
table.getColumnModel().getColumn(9).setPreferredWidth(150);
table.getColumnModel().getColumn(10).setPreferredWidth(150);
table.getColumnModel().getColumn(11).setPreferredWidth(150);
table.getTableHeader().setResizingAllowed(false);
table.getTableHeader().setReorderingAllowed(false);
JScrollPane scrollPane = new JScrollPane(table);
btnAdd = new JButton("Add Student");
btnAdd.addActionListener(bh);
btnEdit = new JButton("EDIT");
btnEdit.addActionListener(bh);
btnEdit.setEnabled(false);
btnDelete = new JButton("DELETE");
btnDelete.addActionListener(bh);
btnDelete.setEnabled(false);
btnSort = new JButton("Update");
btnSort.addActionListener(bh);
btnSave = new JButton("SAVE");
btnSave.addActionListener(bh);
btnSave.setActionCommand("Save");
btnAddInput = new JButton("Add Student");
btnAddInput.addActionListener(bh);
btnAddInput.setActionCommand("AddInput");
btnCancel = new JButton("Cancel");
btnCancel.addActionListener(bh);
labelID = new JLabel("ID");
labelName = new JLabel("NAME");
labelMajor = new JLabel("Major");
labelGPA = new JLabel("GPA");
labelCampus = new JLabel("Campus");
labelAddress = new JLabel("Address");
labelPhone = new JLabel("Phone Number");
labelEmail = new JLabel("Email");
labelCurrent = new JLabel("Current CST courses");
labelPast = new JLabel("Past CST courses");
labelFuture = new JLabel("Future CST courses");
labelNotes = new JLabel("Notes");
txtID = new JTextField(20);
txtName = new JTextField(20);
txtMajor = new JTextField(20);
txtGPA = new JTextField(20);
txtCampus = new JTextField(20);
txtAddress = new JTextField(20);
txtPhone = new JTextField(20);
txtEmail = new JTextField(20);
txtCurrent = new JTextField(20);
txtPast = new JTextField(20);
txtFuture = new JTextField(20);
txtNotes = new JTextField(20);
txtID.setDocument(new IAdvise.JTextFieldLimit(8));
txtID.addKeyListener(keyListener);
tablePanel = new JPanel();
tablePanel.setLayout(new BoxLayout(tablePanel, BoxLayout.PAGE_AXIS));
tablePanel.setBorder(BorderFactory.createEmptyBorder(10, 2, 0, 10));
tablePanel.add(table.getTableHeader());
tablePanel.add(table);
JScrollPane jScrollPane = new JScrollPane(tablePanel);
scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_NEVER);
scrollPane.setBounds(50, 30, 300, 50);
JPanel contentPane = new JPanel(null);
contentPane.setPreferredSize(new Dimension(500, 400));
contentPane.add(scrollPane);
buttonPanel = new JPanel();
buttonPanel.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
c.gridx = 0;
c.gridy = 0;
c.ipady = 20;
c.insets = new Insets(10, 10, 10, 10);
c.fill = GridBagConstraints.HORIZONTAL;
buttonPanel.add(btnAdd, c);
c.gridx = 0;
c.gridy = 1;
c.fill = GridBagConstraints.HORIZONTAL;
c.ipady = 20;
c.insets = new Insets(10, 10, 10, 10);
buttonPanel.add(btnEdit, c);
c.gridx = 0;
c.gridy = 2;
c.fill = GridBagConstraints.HORIZONTAL;
c.ipady = 20;
c.insets = new Insets(10, 10, 10, 10);
buttonPanel.add(btnDelete, c);
c.gridx = 0;
c.gridy = 3;
c.ipady = 20;
c.insets = new Insets(10, 10, 10, 10);
c.fill = GridBagConstraints.HORIZONTAL;
buttonPanel.add(btnSort, c);
c.gridx = 0;
c.gridy = 4;
c.ipady = 20;
c.insets = new Insets(10, 10, 10, 10);
c.fill = GridBagConstraints.HORIZONTAL;
buttonPanel.add(btnSave, c);
frame = new JFrame("Tutoring Database");
frame.setVisible(true);
frame.setResizable(false);
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.add(tablePanel, BorderLayout.CENTER);
frame.add(buttonPanel, BorderLayout.EAST);
frame.pack();
addPanel = new JPanel();
addPanel.setLayout(new GridBagLayout());
c.insets = new Insets(1, 0, 1, 1);
c.gridx = 0;
c.gridy = 0;
addPanel.add(labelID, c);
c.gridy = 1;
addPanel.add(labelName, c);
c.gridy = 2;
addPanel.add(labelMajor, c);
c.gridy = 3;
addPanel.add(labelGPA, c);
c.gridy = 4;
addPanel.add(labelCampus, c);
c.gridy = 5;
addPanel.add(labelAddress, c);
c.gridy = 6;
addPanel.add(labelPhone, c);
c.gridy = 7;
addPanel.add(labelEmail, c);
c.gridy = 8;
addPanel.add(labelCurrent, c);
c.gridy = 9;
addPanel.add(labelPast, c);
c.gridy = 10;
addPanel.add(labelFuture, c);
c.gridy = 11;
addPanel.add(labelNotes, c);
// text fields
c.gridx = 1;
c.gridy = 0;
c.ipady = 1;
addPanel.add(txtID, c);
c.gridy = 1;
c.ipady = 1;
addPanel.add(txtName, c);
c.gridy = 2;
c.ipady = 1;
addPanel.add(txtMajor, c);
c.gridy = 3;
c.ipady = 1;
addPanel.add(txtGPA, c);
c.gridy = 4;
c.ipady = 1;
addPanel.add(txtCampus, c);
c.gridy = 5;
c.ipady = 1;
addPanel.add(txtAddress, c);
c.gridy = 6;
c.ipady = 1;
addPanel.add(txtPhone, c);
c.gridy = 7;
c.ipady = 1;
addPanel.add(txtEmail, c);
c.gridy = 8;
c.ipady = 1;
addPanel.add(txtCurrent, c);
c.gridy = 9;
c.ipady = 1;
addPanel.add(txtPast, c);
c.gridy = 10;
c.ipady = 1;
addPanel.add(txtFuture, c);
c.gridy = 11;
c.ipady = 1;
addPanel.add(txtNotes, c);
buttonPanel2 = new JPanel();
buttonPanel2.setLayout(new GridLayout(1, 1));
buttonPanel2.add(btnAddInput);
buttonPanel2.add(btnCancel);
frame1 = new JFrame("Student Database");
frame1.setVisible(false);
frame1.setResizable(false);
frame1.setDefaultCloseOperation(HIDE_ON_CLOSE);
frame1.add(addPanel, BorderLayout.CENTER);
frame1.add(buttonPanel2, BorderLayout.PAGE_END);
frame1.pack();
}// end
KeyListener keyListener = new KeyListener() {
@Override
public void keyTyped(KeyEvent e) {
}
@Override
public void keyPressed(KeyEvent e) {
keyCode = e.getKeyCode();
if (!(keyCode >= 48 && keyCode <= 57) && !(keyCode >= 96 && keyCode <= 105)
&& !(keyCode >= 37 && keyCode <= 40) && !(keyCode == 127 || keyCode == 8)) {
txtID.setEditable(false);
}
}
@Override
public void keyReleased(KeyEvent e) {
txtID.setEditable(true);
}
};
class RowListener implements ListSelectionListener {
@Override
public void valueChanged(ListSelectionEvent event) {
if (event.getValueIsAdjusting()) {
rowIndex = table.getSelectedRow();
if (data[rowIndex][0] == null || data[rowIndex][0] == "") {
btnEdit.setEnabled(false);
btnDelete.setEnabled(false);
} else {
btnEdit.setEnabled(true);
btnDelete.setEnabled(true);
}
}
}
}
class ButtonHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (e.getActionCommand().equals("Add Student")) {
txtID.setText("");
txtName.setText("");
txtMajor.setText("");
txtGPA.setText("");
txtCampus.setText("");
txtAddress.setText("");
txtPhone.setText("");
txtEmail.setText("");
txtCurrent.setText("");
txtPast.setText("");
txtFuture.setText("");
txtNotes.setText("");
Student student = new Student(txtID.getText(), txtName.getName(), txtMajor.getText(), txtGPA.getText(), txtCampus.getText(), txtAddress.getText(), txtPhone.getText(),txtEmail.getText(), txtCurrent.getText(), txtPast.getText(), txtFuture.getText(), txtNotes.getText());
al.add(student);
frame1.setTitle("Add Student data"); // title bar name for add
frame1.setVisible(true);
} else if (e.getActionCommand().equals("EDIT")) {
txtID.setText(data[rowIndex][0] + "");
txtName.setText(data[rowIndex][1] + "");
txtMajor.setText(data[rowIndex][2] + "");
txtGPA.setText(data[rowIndex][3] + "");
txtCampus.setText(data[rowIndex][4] + "");
txtAddress.setText(data[rowIndex][5] + "");
txtPhone.setText(data[rowIndex][6] + "");
txtEmail.setText(data[rowIndex][7] + "");
txtCurrent.setText(data[rowIndex][8] + "");
txtPast.setText(data[rowIndex][9] + "");
txtFuture.setText(data[rowIndex][10] + "");
txtNotes.setText(data[rowIndex][11] + "");
txtID.setEditable(false);
frame1.setTitle("Enter Student data");
btnAddInput.setActionCommand("Edit2");
btnAddInput.setText("ACCEPT");
frame1.setVisible(true);
} else if (e.getActionCommand().equals("DELETE")) {
int confirm = JOptionPane.showConfirmDialog(frame, "ARE YOU SURE?", "CONFIRM",
JOptionPane.YES_NO_OPTION);
if (confirm == 0) {
rowIndex = table.getSelectedRow();
rowNumber = 0;
noOfStudents--;
for (int i = 0; i <= 10; i++) {
if (rowIndex != i && i <= noOfStudents) {
data[rowNumber][0] = data[i][0];
data[rowNumber][1] = data[i][1];
data[rowNumber][2] = data[i][2];
data[rowNumber][3] = data[i][3];
data[rowNumber][4] = data[i][4];
data[rowNumber][5] = data[i][5];
data[rowNumber][6] = data[i][6];
data[rowNumber][7] = data[i][7];
data[rowNumber][8] = data[i][8];
data[rowNumber][9] = data[i][9];
data[rowNumber][10] = data[i][10];
data[rowNumber][11] = data[i][11];
rowNumber++;
} else if (rowIndex != i && i > noOfStudents) {
data[rowNumber][0] = "";
data[rowNumber][1] = "";
data[rowNumber][2] = "";
data[rowNumber][3] = "";
data[rowNumber][4] = "";
data[rowNumber][5] = "";
data[rowNumber][6] = "";
data[rowNumber][7] = "";
data[rowNumber][8] = "";
data[rowNumber][9] = "";
data[rowNumber][10] = "";
data[rowNumber][11] = "";
rowNumber++;
}
}
if (noOfStudents == 1000) {
btnAdd.setEnabled(false);
}
else {
btnAdd.setEnabled(true);
}
if (noOfStudents == 0) {
btnDelete.setEnabled(false);
btnEdit.setEnabled(false);
} else {
btnDelete.setEnabled(true);
btnEdit.setEnabled(true);
}
rowIndex = table.getSelectedRow();
if (data[rowIndex][0] == null || data[rowIndex][0] == "") {
btnEdit.setEnabled(false);
btnDelete.setEnabled(false);
} else {
btnEdit.setEnabled(true);
btnDelete.setEnabled(true);
}
table.updateUI();
}
} else if (e.getActionCommand().equals("AddInput")) {
if (txtID.getText().isEmpty() || txtName.getText().isEmpty()
|| txtMajor.getText().isEmpty()// /
|| txtGPA.getText().isEmpty() || txtCampus.getText().isEmpty()|| txtEmail.getText().isEmpty()
|| txtCurrent.getText().isEmpty()|| txtPast.getText().isEmpty()|| txtFuture.getText().isEmpty()
|| txtNotes.getText().isEmpty() || txtPhone.getText().isEmpty()) {
JOptionPane.showMessageDialog(null, "PLEASE FILL IN THE BLANKS.", "ERROR!",
JOptionPane.ERROR_MESSAGE);
}
else {
int dup = 0;
for (int i = 0; i < 8; i++) {
if (txtID.getText().equals(data[i][0])) {
JOptionPane.showMessageDialog(null, "ID NUMBER ALREADY EXISTS.", "ERROR!",
JOptionPane.ERROR_MESSAGE);
dup++;
}
}
if (dup == 0) {
rowIndex = table.getSelectedRow();
data[noOfStudents][0] = txtID.getText();
data[noOfStudents][1] = txtName.getText();
data[noOfStudents][2] = txtMajor.getText();
data[noOfStudents][3] = txtGPA.getText();
data[noOfStudents][4] = txtCampus.getText();
data[noOfStudents][5] = txtAddress.getText();
data[noOfStudents][6] = txtPhone.getText();
data[noOfStudents][7] = txtEmail.getText();
data[noOfStudents][8] = txtCurrent.getText();
data[noOfStudents][9] = txtPast.getText();
data[noOfStudents][10] = txtFuture.getText();
data[noOfStudents][11] = txtNotes.getText();
table.updateUI();
frame1.dispose();
noOfStudents++;
if (noOfStudents == 50){
btnAdd.setEnabled(false);
}
else {
btnAdd.setEnabled(true);
}
if (data[rowIndex][0] == null) {
btnEdit.setEnabled(false);
btnDelete.setEnabled(false);
} else {
btnEdit.setEnabled(true);
btnDelete.setEnabled(true);
}
}
}
table.updateUI();
}else if(e.getActionCommand().equals("Save")){
try {
PrintWriter out = new PrintWriter("Tutor.txt");
for(int i = 0; i < 25; i++)
{
for(int j = 0; j < 10; j++)
{
out.print(data[i][j]);
out.print(", ");
if(j == 10){
out.println();
}
} out.flush();
}} catch (FileNotFoundException ex) {
}
} else if (e.getActionCommand().equals("Update")) {
}
if (txtID.getText().isEmpty() || txtName.getText().isEmpty()
|| txtMajor.getText().isEmpty()// /
|| txtGPA.getText().isEmpty() || txtCampus.getText().isEmpty()|| txtEmail.getText().isEmpty()
|| txtCurrent.getText().isEmpty()|| txtPast.getText().isEmpty()|| txtFuture.getText().isEmpty()
|| txtNotes.getText().isEmpty()) {
} else {
data[rowIndex][0] = txtID.getText();
data[rowIndex][1] = txtName.getText();
data[rowIndex][2] = txtMajor.getText();
data[rowIndex][3] = txtGPA.getText();
data[rowIndex][4] = txtCampus.getText();
data[rowIndex][5] = txtAddress.getText();
data[rowIndex][6] = txtPhone.getText();
data[rowIndex][7] = txtEmail.getText();
data[rowIndex][8] = txtEmail.getText();
data[rowIndex][9] = txtEmail.getText();
data[rowIndex][10] = txtEmail.getText();
data[rowIndex][11] = txtEmail.getText();
frame1.dispose();
}
table.updateUI();
}
}
class JTextFieldLimit extends PlainDocument {
private int limit;
JTextFieldLimit(int limit) {
super();
this.limit = limit;
}
JTextFieldLimit(int limit, boolean upper) {
super();
this.limit = limit;
}
@Override
public void insertString(int offset, String str, AttributeSet attr)
throws BadLocationException {
if (str == null) {
return;
}
if ((getLength() + str.length()) <= limit) {
super.insertString(offset, str, attr);
}
}
}
public static void main(String[] args) {
new IAdvise();
}
}
学生班:
public class Student implements java.io.Serialize{
private final String id;
private final String name;
private final String major;
private final String gpa;
private final String campus;
private final String address;
private final String number;
private final String email;
private final String current;
private final String past;
private final String future;
public Student(String id, String name, String major,String gpa, String campus, String address,String number, String email, String current, String past, String future, String notes) {
this.id = id;
this.name = name;
this.major = major;
this.gpa = gpa;
this.campus = campus;
this.address = address;
this.number = number;
this.email = email;
this.current = current;
this.past = past;
this.future = future;
}
}
推荐答案
将使用数组的代码更改为使用 ArrayList 的代码:
To change code that uses an array into code that uses an ArrayList:
代替
a[i]，当它不在赋值的左侧时，使用a.get(i)
Instead of
a[i], when it's not on the left side of an assignment, usea.get(i)
使用a.size()
而不是设置 a[i] = expression:如果 i 已知在范围内 (0 <= i> <= a.length-1)，使用a.set(i, expression).如果 i == a.length，则不能将 a[i] = expression 与数组一起使用，但可以使用 ArrayList，将大小增加 1:a.add(expression).如果 i >a.length，这样你就想在ArrayList中添加一个新的元素留一个空隙，然后是这样的:
Instead of setting a[i] = expression: if i is known to be in range (0 <= i <= a.length-1), use a.set(i, expression). If i == a.length, you couldn't use a[i] = expression with an array, but you can do it with an ArrayList, increasing the size by 1: a.add(expression). If i > a.length, so that you want to add a new element in the ArrayList leaving a gap, then something like:
while (a.size() < i)
a.add (null);
// at this point a.size == i
a.add (expression);
// now a.size == i+1
这应该涵盖对数组的所有基本操作.Arrays 中定义的一些实用操作在 ArrayList 中没有等效操作，例如 binarySearch.
That should cover all the basic operations on arrays. There are some utility operations defined in Arrays that don't have equivalent operations in ArrayList, like binarySearch.
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