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Question

这是我的项目:

package myProjects;
import java.awt.GridBagConstraints;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.*;
public class GeometryEquationSolver extends JFrame{
JPanel mainPanel;
JTextField eq1Text, eq2Text;
JButton enterButton, clearTextButton;
public static void main(String[] args) {
    new GeometryEquationSolver();
}
public GeometryEquationSolver(){
    this.setSize(340, 140);
    this.setTitle("Equation Solver");
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    this.setLocationRelativeTo(null);
    mainPanel = new JPanel();
    mainPanel.setLayout(new GridBagLayout());
    addItem(new JLabel("Equation 1"), 0, 0, 1, 1);
    addItem(new JLabel("Equation 2"), 2, 0, 1, 1);
    eq1Text = new JTextField(10);
    addItem(eq1Text, 0, 1, 1, 1);
    eq2Text = new JTextField(10);
    addItem(eq2Text, 2, 1, 1, 1);
    addItem(new JLabel("="), 1, 1, 1, 1); // Just the "=" for looks.
    enterButton = new JButton("Enter");
    enterButton.addActionListener(e->{
        Equation eq1 = new Equation(eq1Text.getText());
    });
    addItem(enterButton, 0, 2, 1, 1);
    clearTextButton = new JButton("Clear");
    clearTextButton.addActionListener(e->{
        eq1Text.setText(null);
        eq2Text.setText(null);
    });
    addItem(clearTextButton, 2, 2, 1, 1);
    this.add(mainPanel);
    this.setVisible(true);
}
private String[] rawData;
private String[] splitEq(String eq){
    rawData = eq.split("");
    return rawData;
}
private void addItem(JComponent c, int x, int y, int width, int height){
    GridBagConstraints gbc = new GridBagConstraints();
    gbc.gridx = x;
    gbc.gridy = y;
    gbc.gridwidth = width;
    gbc.gridheight = height;
    gbc.weightx = 100.0;
    gbc.weighty = 100.0;
    gbc.fill = GridBagConstraints.NONE;
    mainPanel.add(c, gbc);
}
}
class Equation{
public enum opperation {add, sub, mult, div};
public opperation opper;
public String eq;
public Equation(String eq){
    this.eq = eq;
    opper = opperation.add;
    this.Equation(this.eq, opper);
}
 public Equation(String eq, opperation opper){
    }
}

我的问题发生在类方程。在第一个构造函数中，我必须如下行:

this.Equation(this.eq, opper);

我得到这个错误:

方法Equation(String, Equation. operation)对于类型Equation

是未定义的

我试图在第一个构造函数之后调用构造函数。有人知道怎么解决这个问题吗?

Answer 1

正确的语法应该是this(this.eq, opper);。然而，由于这行必须是构造函数代码中的第一行，因此它将变成this(eq, opperation.add);。

所以你的构造函数最终会是这样的:

public Equation(String eq){
    this(eq, opperation.add);
    this.eq = eq;
    opper = opperation.add;
    //this.Equation(this.eq, opper);
}

如果绝对有必要在调用另一个构造函数之前执行一些代码，那么这个答案可能会有所帮助。

Answer 2

如果您想从构造函数中调用构造函数，请参阅https://docs.oracle.com/javase/tutorial/java/javaOO/thiskey.html

下面是可以工作的代码。

public class Equation {
    public static enum opperation {add, sub, mult, div};
    public opperation opper;
    public String eq;
    public Equation(String eq){
        this(eq, opperation.add);
        this.eq = eq;
        opper = opperation.add;
    }
    public Equation(String eq, opperation opper){
    }
}