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问题描述
import java.awt.*;导入 java.awt.event.*;公共类 QuadraticSolver 扩展 Frame 实现 ActionListener、WindowListener{私人文本字段 tfX2；私人文本字段 tfX；私人文本字段 tfNum;私人文本字段 tfVal1；私人文本字段 tfVal2；私人文本字段 tfRoots;私人标签 lblX2；私人标签 lblX；私人标签 lblNum;私有标签 lblVal1；私人标签 lblVal2；私人标签 lblRoots;私人按钮 btnCheckRoots;私人按钮 btnCalc;私人按钮 btnClear;双 a = 0, b = 0, c = 0;双Val1 = 0，Val2 = 0，判别式= 0；字符串 StrVal1, StrVal2;公共 QuadraticSolver(){Panel panelX2Comp = new Panel(new FlowLayout());{lblX2 = new Label("输入X^2的系数:");panelX2Comp.add (lblX2);tfX2 = new TextField("", 20);tfX2.setEditable(true);panelX2Comp.add(tfX2);}Panel panelXComp = new Panel(new FlowLayout());{lblX = new Label("输入X的系数:");panelXComp.add(lblX);tfX = new TextField("", 20);tfX.setEditable(true);panelXComp.add(tfX);}Panel panelNumComp = new Panel(new FlowLayout());{lblNum = new Label("请输入数字:");panelNumComp.add(lblNum);tfNum = new TextField("", 20);tfNum.setEditable(true);panelNumComp.add(tfNum);}Panel panelButtons = new Panel(new FlowLayout());{btnCalc = new Button("计算");btnCalc.setEnabled(false);panelButtons.add(btnCalc);{btnCalc.addActionListener(new ActionListener(){@覆盖public void actionPerformed(ActionEvent e){a = Double.parseDouble(tfX2.getText());b = Double.parseDouble(tfX.getText());c = Double.parseDouble(tfNum.getText());Val1 = (-b + Math.sqrt(判别式))/(2 * a);Val2 = (-b - Math.sqrt(判别式))/(2 * a);StrVal1 = String.valueOf(Val1);StrVal2 = String.valueOf(Val2);tfVal1.setText(StrVal1);tfVal2.setText(StrVal2);tfX2.setText("");tfX.setText("");tfNum.setText("");btnCalc.setEnabled(false);}});}btnCheckRoots = new Button("根的性质");panelButtons.add(btnCheckRoots);{btnCheckRoots.addActionListener(new ActionListener(){@覆盖public void actionPerformed(ActionEvent e){a = Double.parseDouble(tfX2.getText());b = Double.parseDouble(tfX.getText());c = Double.parseDouble(tfNum.getText());判别式 = (b*b) - (4*(a*c));如果(判别式== 0){tfRoots.setText("相等");btnCalc.setEnabled(true);}否则如果(判别式这是我的代码.它给我一个错误说QuadraticSolver.java:4: error: QuadraticSolver 不是 abstract 并且不会覆盖抽象方法 actionPerformed(ActionEvent)在 ActionListenerpublic class QuadraticSolver extends Frame 实现 ActionListener, WindowListener"
我不知道该怎么办.我尝试在所有 ActionListener 事件之前添加 @Override，仍然不起作用.
解决方案
既然 QuadraticSolver 实现了 ActionListener，它应该实现 actionPerformed.>
您在匿名类中实现了该方法.
要解决此问题，请将 actionPerformed 的实现添加到 QuadraticSolver 或不需要 QuadraticSolver 来实现该接口.
import java.awt.*;
import java.awt.event.*;
public class QuadraticSolver extends Frame implements ActionListener, WindowListener
{
private TextField tfX2;
private TextField tfX;
private TextField tfNum;
private TextField tfVal1;
private TextField tfVal2;
private TextField tfRoots;
private Label lblX2;
private Label lblX;
private Label lblNum;
private Label lblVal1;
private Label lblVal2;
private Label lblRoots;
private Button btnCheckRoots;
private Button btnCalc;
private Button btnClear;
double a = 0, b = 0, c = 0;
double Val1 = 0, Val2 = 0, Discriminant = 0;
String StrVal1, StrVal2;
public QuadraticSolver()
{
Panel panelX2Comp = new Panel(new FlowLayout());
{
lblX2 = new Label("Enter Co-Efficient Of X^2:");
panelX2Comp.add (lblX2);
tfX2 = new TextField("", 20);
tfX2.setEditable(true);
panelX2Comp.add(tfX2);
}
Panel panelXComp = new Panel(new FlowLayout());
{
lblX = new Label("Enter Co-Efficient Of X:");
panelXComp.add(lblX);
tfX = new TextField("", 20);
tfX.setEditable(true);
panelXComp.add(tfX);
}
Panel panelNumComp = new Panel(new FlowLayout());
{
lblNum = new Label("Enter Number:");
panelNumComp.add(lblNum);
tfNum = new TextField("", 20);
tfNum.setEditable(true);
panelNumComp.add(tfNum);
}
Panel panelButtons = new Panel(new FlowLayout());
{
btnCalc = new Button("Calculate");
btnCalc.setEnabled(false);
panelButtons.add(btnCalc);
{
btnCalc.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent e)
{
a = Double.parseDouble(tfX2.getText());
b = Double.parseDouble(tfX.getText());
c = Double.parseDouble(tfNum.getText());
Val1 = (-b + Math.sqrt(Discriminant)) / (2 * a);
Val2 = (-b - Math.sqrt(Discriminant)) / (2 * a);
StrVal1 = String.valueOf(Val1);
StrVal2 = String.valueOf(Val2);
tfVal1.setText(StrVal1);
tfVal2.setText(StrVal2);
tfX2.setText("");
tfX.setText("");
tfNum.setText("");
btnCalc.setEnabled(false);
}
}
);
}
btnCheckRoots = new Button("Nature Of Roots");
panelButtons.add(btnCheckRoots);
{
btnCheckRoots.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent e)
{
a = Double.parseDouble(tfX2.getText());
b = Double.parseDouble(tfX.getText());
c = Double.parseDouble(tfNum.getText());
Discriminant = (b*b) - (4*(a*c));
if (Discriminant == 0)
{
tfRoots.setText("Equal");
btnCalc.setEnabled(true);
}
else if (Discriminant < 0)
{
tfRoots.setText("Imaginary");
}
else
{
tfRoots.setText("Real, Distinct");
btnCalc.setEnabled(true);
}
}
}
);
}
btnClear = new Button("Clear");
panelButtons.add(btnClear);
{
btnClear.addActionListener(new ActionListener()
{
@Override
public void actionPerformed(ActionEvent e)
{
a = 0; b = 0; c = 0;
Val1 = 0; Val2 = 0; Discriminant = 0;
tfX2.setText("");
tfX.setText("");
tfNum.setText("");
tfVal1.setText("");
tfVal2.setText("");
tfRoots.setText("");
}
}
);
}
}
Panel panelRoots = new Panel(new FlowLayout());
{
lblRoots = new Label ("Nature Of Roots:");
panelRoots.add(lblRoots);
tfRoots = new TextField("", 20);
tfRoots.setEditable(false);
panelRoots.add(tfRoots);
}
Panel panelValues = new Panel(new FlowLayout());
{
lblVal1 = new Label("First Value:");
panelValues.add(lblVal1);
tfVal1 = new TextField("", 10);
tfVal1.setEditable(false);
panelValues.add(tfVal1);
lblVal2 = new Label("Second Value:");
panelValues.add(lblVal2);
tfVal2 = new TextField("", 10);
tfVal2.setEditable(false);
panelValues.add(tfVal2);
}
setLayout(new FlowLayout()); // "this" Frame sets to BorderLayout
add(panelX2Comp);
add(panelXComp);
add(panelNumComp);
add(panelButtons);
add(panelRoots);
add(panelValues);
setTitle("Matrix Multiplier"); // "this" Frame sets title
setSize(400, 200); // "this" Frame sets initial size
setVisible(true);
addWindowListener(this);
}
@Override
public void windowClosing(WindowEvent e)
{
System.exit(0); // Terminate the program
}
@Override
public void windowOpened(WindowEvent e) { }
@Override
public void windowClosed(WindowEvent e) { }
@Override
public void windowIconified(WindowEvent e) { }
@Override
public void windowDeiconified(WindowEvent e) { }
@Override
public void windowActivated(WindowEvent e) { }
@Override
public void windowDeactivated(WindowEvent e) { }
public static void main(String args[])
{
new QuadraticSolver();
}
}
So this is my code. it give me an error saying "QuadraticSolver.java:4: error: QuadraticSolver is not abstract and does not override abstract method actionPerformed(ActionEvent) in ActionListenerpublic class QuadraticSolver extends Frame implements ActionListener, WindowListener"
I have no idea what to do. I tried adding @Override before all ActionListener events, Still doesn't work.
解决方案
Since QuadraticSolver implements ActionListener, it should implement actionPerformed.
You implemented that method in an anonymous class.
To solve it, either add an implementation of actionPerformed to QuadraticSolver or don't require QuadraticSolver to implement that interface.
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