我有一个关于java初始化的问题，我不知道为什么java认为我的程序中的double没有初始化，即使我已经初始化它。有人可以向我解释如何解决这个问题吗？在下面的代码中，java表示双“inC”未初始化。
package tempconverter;
import java.awt.Color;
import javax.swing.*;
import java.awt.event.*;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.BorderLayout;
public class TempConverter extends JFrame implements ActionListener, ItemListener
{
static String[] choices = { "From Celsius", "From Fahrenheit", "From Kelvin", "From Rankine" };
static JFrame f = new JFrame("Temperature Converter");
static JTextField enter = new JTextField(5);
static JButton confirm = new JButton("Convert");
static JComboBox choose = new JComboBox(choices);
static JFrame tell = new JFrame();
static JLabel one = new JLabel();
static JLabel two = new JLabel();
static JLabel three = new JLabel();
public static void main(String[] args)
{
Font main = new Font("Comic Sans", Font.PLAIN, 12);
confirm.addActionListener(new TempConverter());
confirm.setFont(main);
choose.setFont(main);
enter.setFont(main);
choose.addItemListener(new TempConverter());
f.setBackground(Color.WHITE);
f.setLayout(new FlowLayout());
f.setSize(340, 60);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(enter);
f.add(confirm);
f.add(choose);
tell.setLayout(new BorderLayout());
tell.add(one, BorderLayout.NORTH);
tell.add(two, BorderLayout.WEST);
tell.add(three, BorderLayout.SOUTH);
tell.setSize(160, 65);
tell.setLocationRelativeTo(null);
f.setVisible(true);
}
@Override
public void actionPerformed(ActionEvent e)
{
double toConvert = Double.parseDouble(enter.getText());
double inF, inK, inC, tempF = 0, tempK, inR, tempR;
double tempC;
if (choose.getSelectedItem().equals("From Celsius"))
{
tempF = toConvert * 1.8 + 32;
tempK = toConvert + 273.15;
tempR = (toConvert + 273.15) * 1.8;
inF = Math.round(tempF * 100.00) / 100.00;
inK = Math.round(tempK * 100.00) / 100.00;
inR = Math.round(tempR * 100.00) / 100.00;
one.setText(toConvert + "°C = " + inF + "°F");
two.setText(toConvert + "°C = " + inK + "°K");
three.setText(toConvert + "°C = " + inR + "°R");
tell.setVisible(true);
}
if (choose.getSelectedItem().equals("From Fahrenheit"))
{
if (toConvert == 32)
{
inC = 0;
inK = 273.15;
inR = toConvert + 459.67;
one.setText(toConvert + "°F = " + inC + "°C");
two.setText(toConvert + "°F = " + inK + "°K");
three.setText(toConvert + "°F = " + inR + "°R");
}
else
tempC = (toConvert - 32) / 1.8;
tempK = (toConvert - 32) / 1.8 + 273.15;
tempR = toConvert + 459.67;
inC = Math.round(tempC * 100.00) / 100.00;
inK = Math.round(tempK * 100.00) / 100.00;
inR = Math.round(tempR * 100.00) / 100.00;
one.setText(toConvert + "°F = " + inC + "°C");
two.setText(toConvert + "°F = " + inK + "°K");
three.setText(toConvert + "°F = " + inR + "°R");
tell.setVisible(true);
}
if (choose.getSelectedItem().equals("From Kelvin"))
{
tempC = toConvert - 273.15;
tempF = tempC * 1.8 + 32;
tempR = toConvert * 1.8;
inC = Math.round(tempC * 100.00) / 100.00;
inF = Math.round(tempF * 100.00) / 100.00;
inR = Math.round(tempR * 100.00) / 100.00;
one.setText(toConvert + "°K = " + inC + "°C");
two.setText(toConvert + "°K = " + inF + "°F");
three.setText(toConvert + "°K = " + inR + "°R");
tell.setVisible(true);
}
if (choose.getSelectedItem().equals("From Rankine"))
{
if (toConvert == 0)
{
tempF = toConvert - 459.67;
tempK = toConvert * (5 / 9);
inF = Math.round(tempF * 100.00) / 100.00;
inR = Math.round(tempK * 100.00) / 100.00;
one.setText("0°R = -273.15°C");
two.setText("0°R = " + inF + "°F");
three.setText("0°R = " + inR + "°K");
tell.setVisible(true);
}
else
tempC = (toConvert - 491.67) * (5 / 9);
tempF = toConvert - 459.67;
tempK = toConvert * (5 / 9);
inC = Math.round(tempC * 100.00) / 100.00;
inF = Math.round(tempF * 100.00) / 100.00;
inR = Math.round(tempK * 100.00) / 100.00;
one.setText(toConvert + "°R = " + inC + "°C");
two.setText(toConvert + "°R = " + inF + "°F");
three.setText(toConvert + "°R = " + inR + "°K");
tell.setVisible(true);
}
}
@Override
public void itemStateChanged(ItemEvent e)
{
repaint();
}
}
Java指出我没有在“From Fahrenheit”和“From Rankine”方法的else语句中初始化“inC”。但是，当我在变量声明中初始化它时，当我尝试在if-else语句和方法中更改它时它不会改变。我该如何解决这个问题？
答案 0 :(得分：3)
我复制了你的例子，我在tempC收到了消息。原因是在else路径上缺少}。
更改：
else
tempC = (toConvert - 491.67) * (5 / 9);
tempF = toConvert - 459.67;
tempK = toConvert * (5 / 9);
inC = Math.round(tempC * 100.00) / 100.00;
inF = Math.round(tempF * 100.00) / 100.00;
inR = Math.round(tempK * 100.00) / 100.00;
one.setText(toConvert + "°R = " + inC + "°C");
two.setText(toConvert + "°R = " + inF + "°F");
three.setText(toConvert + "°R = " + inR + "°K");
tell.setVisible(true);
TO：
else {
tempC = (toConvert - 491.67) * (5 / 9);
tempF = toConvert - 459.67;
tempK = toConvert * (5 / 9);
inC = Math.round(tempC * 100.00) / 100.00;
inF = Math.round(tempF * 100.00) / 100.00;
inR = Math.round(tempK * 100.00) / 100.00;
one.setText(toConvert + "°R = " + inC + "°C");
two.setText(toConvert + "°R = " + inF + "°F");
three.setText(toConvert + "°R = " + inR + "°K");
tell.setVisible(true);
}
答案 1 :(得分：0)
如上所述，最简单的方法是在声明它时简单地为其赋值。
Java认为它尚未初始化的原因是它实际上可能没有。您只需在4个最外层if语句之一中为其赋值。如果这四个条件都不成立，则永远不会初始化变量。
正如Jens所指出的那样，你错过了{＆＃34; else＆＃34;。
答案 2 :(得分：0)
错误的实际原因是沉闷的：你错过了一个大括号。
但是，让我们看一下tempK = toConvert * (5 / 9);。这不会做你想要的，因为（5/9）将评估为0，因为括号表示这是自己评估的，是整数算术。要解决这个问题，最简单的方法是删除括号：
tempK = toConvert * 5 / 9;
所以一切都是以浮点计算的。 （请注意，*和/具有相同的优先级。）
您在程序中多次出现此错误。