我一直在谷歌搜索解决这个问题的方法，我可能已经找到了，但我对编程很陌生，所以我的理解水平充其量只是平庸。
我在两个JTextField个对象中进行计算，将两个输入值相乘，并将第三个文本字段的文本设置为答案。进行十进制计算时，我希望它只显示两位小数。
我添加了整个代码而不是摘要。
以下是代码：
public class Decorator implements ActionListener
{
JFrame fDecorator; // Declare Decorator frame
JLabel lSize, lType, lTotal, lPrice, lx, lEquals; // Declare Labels
JTextField tLength, tWidth, tSize, tTotal; // Declare JTextFields
JComboBox<String> cbFlooring; //Declare JComboBox
JButton bCalculate1, bCalculate2, bHelp; // Declare JButtons
static double priceTotal, floorPrice, floorSize; // Declare double variables
Decorator()
{
String[] type_floor = new String[] // Create an array called Type_Floor
{" Select ","Wood £0.24", "Ceramic £0.37", "Stone £0.86", "Lino £1.24", "Marble £1.76",
"Laminate £2.10", "Bamboo £2.34", "Carpet £3.78"}; // Add array names for JComboBox
fDecorator = new JFrame("Flooring Decorator"); // Add the Frame
fDecorator.setResizable(false); // Disallow user resizing of frame
fDecorator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
lSize = new JLabel("Input Size of your room (Meters): "); // Add size of floor Label
lType = new JLabel("Type of flooring: "); // Add type of flooring Label
lTotal = new JLabel("Total Price = "); // Add Total price of flooring Label
lx = new JLabel("x"); // Add x Label
lEquals = new JLabel("="); // Add equals Label
lPrice = new JLabel ("Price of floor per square Meter"); // Adds Price Label
bCalculate1 = new JButton("Calculate"); // Add calculate Button
bCalculate2 = new JButton("Calculate"); // Add calculate Button
bHelp = new JButton("Help"); // Add Help Button
tLength = new JTextField(5); // Add user editable Text Field
tWidth = new JTextField(5); // Add second user editable Text Field
tSize = new JTextField(5); // Add total size of room Text Field
tTotal = new JTextField(5); // Add total price Text Field
tTotal.setEditable(false); // Disallow editing of tTotal
tSize.setEditable(false); // Disallow editing of tSize
cbFlooring = new JComboBox<>(type_floor); // Add ComboBox, and type cast Array
fDecorator.setLayout(new FlowLayout()); // Set the layout of Decorator to FlowLayout
fDecorator.add(lSize); // Add Size Label
fDecorator.add(tLength); // Add Entry1 TextField
fDecorator.add(lx); // Add x Label
fDecorator.add(tWidth); // Add Entry2 TextField
fDecorator.add(lEquals); // Add Equals Label
fDecorator.add(tSize); // Add Size TextField
fDecorator.add(bCalculate1); // Add Calculator1 Button
fDecorator.add(lPrice); // Add Price Label
fDecorator.add(cbFlooring); // Add Flooring ComboBox
fDecorator.add(bCalculate2); // Add Calculator2 Button
fDecorator.add(lTotal); // Add Total Label
fDecorator.add(tTotal); // Add Total TextField
fDecorator.add(bHelp); // Add Help Button
bCalculate1.addActionListener(this); // Adds an action listener to Calculate button
bCalculate2.addActionListener(this); // Adds an action listener to Calculate2 button
bHelp.addActionListener(this); // Adds an action listener to Help button
cbFlooring.addActionListener(this); // Adds action listener to ComboBox
Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
fDecorator.setLocation(dim.width/3-fDecorator.getSize().width/3, dim.height/3-fDecorator.getSize().height/3);
fDecorator.setSize(420, 130); // Set frame size too 400 by 200
fDecorator.setVisible(true); // Set frame to visible
}
@Override
public void actionPerformed(ActionEvent e) // Action Listener
{
try // Handle exceptions with code inside this block
{
JComboBox<String> selectionBox = (JComboBox<String>) e.getSource(); // Declare parameterised ComboBox selectionBox
String selectedFloor = (String) selectionBox.getSelectedItem(); // Declare selectedFloor as string inside ComboBox
if(selectedFloor.equals("Wood £0.24")) // If selected Equals Wood
floorPrice = 0.24; // Assign floorPrice value 0.24
else if(selectedFloor.equals("Ceramic £0.37")) // If selected Equals Ceramic
floorPrice = 0.37; // Assign floorPrice value 0.37
else if(selectedFloor.equals("Stone £0.86")) // If selected Equals Stone
floorPrice = 0.86; // Assign floorPrice value 0.86
else if(selectedFloor.equals("Lino £1.24")) // If selected Equals Lino
floorPrice = 1.24; // Assign floorPrice value 1.24
else if(selectedFloor.equals("Marble £1.76")) // If selected Equals Marble
floorPrice = 1.76; // Assign floorPrice value 1.76
else if(selectedFloor.equals("Laminate £2.10")) // If selected Equals Laminate
floorPrice = 2.10; // Assign floorPrice value 2.10
else if(selectedFloor.equals("Bamboo £2.34")) // If selected Equals Bamboo
floorPrice = 2.34; // Assign floorPrice value 2.34
else if(selectedFloor.equals("Carpet £3.78")) // If selected Equals Carpet
floorPrice = 3.78; // Assign floorPrice value 3.78
}
catch(Exception a) // Handle exception using this
{
// Does nothing if an exception is encountered, prevents program from crashing and handles exception
}
try // Handle exception with code inside this block
{
char[] len1 = tLength.getText().toCharArray(); // Declares a char variable that gets the text from tEntry1
char[] len2 = tWidth.getText().toCharArray(); // Declares a char variable that gets the text from tEntry2
for(int loop1 = 0; loop1 < len1.length; loop1++) // For loop that searches through the TextFields
{
if(len1[loop1] == '-' || len2[loop1] == '-') // If the loop finds a - sign
JOptionPane.showMessageDialog(null,"No Negative numbers please!"); // Displays an error message
}
if (tLength.getText() != null && tWidth.getText() != null) // if TextFields have inputs
{
double length = Double.parseDouble(tLength.getText()); // Gets string from TextField and converts to double
double width = Double.parseDouble(tWidth.getText()); // Gets string from TextField and converts to double
if(e.getSource() == bCalculate1) // When Calculate button is clicked
{
tSize.setText(Double.toString(length * width)); // Times input 1 and 2 to find surface area
}
}
}
catch(Exception ab) // Handle exception using this
{
JOptionPane.showMessageDialog(null,"No Text Please!");// Does nothing if an exception is encountered, prevents program from crashing
}
try // Handle exception with code inside this block
{
if(e.getSource() == bCalculate2) // If Calculate2 button is pressed
{
floorSize = Double.parseDouble(tSize.getText()); // Get text value from tSize and assign value too floorSize
priceTotal = floorPrice * floorSize; // Assign value to priceTotal
tTotal.setText(""+priceTotal); // Set tTotal TextField
}
}
catch(Exception abc) // Handle exceptions using this
{
System.out.println("Exception occured!!!!");// If an exception is encountered, prevents program from crashing and handles exception
}
if(e.getSource() == bHelp)
{
JFrame fHelp = new JFrame("Help Screen"); // Declare JFrame fHelp
JLabel lWelcomeHelp = new JLabel("<html>Welcome to the help screen!<br> This screen will guide you though using my decorator application!<br> Firslty input the length and width into the text fields, then press calculate.<br> This will generate the size of the floor you're going to be decorating.<br>After that select which floor you would like to use,<br>the price for each type of flooring is displayed next to it.<br> After deciding on a floor press the second calculate button to price up your new floor!<html>", SwingConstants.CENTER);
// Declare JLabel WelcomeHelp
fHelp.setLayout(new FlowLayout()); // Set fHelp frame layout as FlowLayout
fHelp.add(lWelcomeHelp); // Add WelcomeHelp JLabel to fHelp frame
fHelp.setSize(600, 250); // Set size of frame
fHelp.setVisible(true); // Make frame visible
}
}
}
答案 0 :(得分：2)
DecimalFormat dc = new DecimalFormat("0.00");
String formattedText = dc.format(yourDouble);
你的文件是想要格式化的双倍。
您可以将不同的字符串传递给DecimalFormat构造函数以获得不同的效果。例如，DecimalFormat("###,###,###.00")会在每3个数字处放置一个逗号，其中要格式化的数字最多为小数点前9位数。
答案 1 :(得分：1)
尝试类似：
DecimalFormat df = new DecimalFormat("#.00");
tSize.setText(Double.toString(df.format(Length * Width)));
答案 2 :(得分：-1)
double length = Double.parseDouble(tLength.getText());
double width = Double.parseDouble(tWidth.getText());
int numberOfDigitsAfterDecimal = 2;
Double yourDoubleResult = length * width;
Double resultToBeShown = new BigDecimal(yourDoubleResult).setScale(numberOfDigitsAfterDecimal, BigDecimal.ROUND_HALF_UP).doubleValue();
System.out.println(resultToBeShown.toString());
if(e.getSource() == bCalculate) {
tSize.setText(resultToBeShown.toString());
}