Question

我的项目应该对多项式进行基本操作。每个多项式都是来自类Monom的对象的ArrayList。我用Swing创建了一个界面。我创建了一个方法，将收到的String转换为Polinom对象。如果我使用基本命令，比如当我按下按钮，获取文本并显示它时，一切正常。但是当我调用前面提到的方法（toPolinom）时，按钮不再起作用，并且在控制台中写入了红线。

这是按钮代码的样子：

 mybutton = new JButton("Suma");
    mybutton.addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent e) {

            String pol1 = numberField1.getText();
            String pol2 = numberField2.getText();
            polinom1 = new Polinom(p1);
            polinom2 = new Polinom(p2);
            polinom1 = polinom1.toPolinom(pol1);
            polinom2 = polinom2.toPolinom(pol2);
            resultField.setText(polinom1.suma(polinom1, polinom2)
                    .toString());       

        }
    }); 

   mybutton2 = new JButton("Diferenta");
    mybutton2.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            String pol1 = numberField1.getText();
            String pol2 = numberField2.getText();
            polinom1 = polinom1.toPolinom(pol1);
            polinom2 = polinom2.toPolinom(pol2);
            resultField.setText(rezultat.diferenta(polinom1, polinom2)
                    .toString());

        }
    });

resultField和numberField1是JTextField类型;

这是toPolinom()课程中的Polinom.java方法：

   public  Polinom toPolinom(String p1) {

    List<Monom> prez = new ArrayList<Monom>();
    int grad, coef;
    int i = 0;
    for(i=0; i<p1.length()-1; i=i+5){
        grad=0; coef=0;
        if(p1.charAt(i)=='+') coef=Character.getNumericValue(p1.charAt(i+1));
        else if (p1.charAt(i)=='-') coef=-Character.getNumericValue(p1.charAt(i+1));
        grad=Character.getNumericValue(p1.charAt(i+4));
        prez.add(new MonomZ(grad, coef));
    }


    return new Polinom(prez);
}

我测试了这种方法，它有效。

最后，这是我点击按钮时收到的内容：

   Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: -1
at java.util.ArrayList.elementData(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at tema1.Polinom.toString(Polinom.java:208)
at tema1.Fatza$1.actionPerformed(Fatza.java:61)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$400(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

警告方法补充道：

  public String toString() {

    String Rezultat = "";
    for (int i = 0; i < polinom.size() - 1; i++) {
        Rezultat = Rezultat + verificare(polinom.get(i), polinom, i);
    }
    return Rezultat
            + verificare(polinom.get(polinom.size() - 1), polinom, //line 208
                    polinom.size() - 1);

}

private String verificare(Monom monom, List<Monom> polinom, int n) {
    // functia verifica daca trebuie adaugat semn sau nu
    String text;
    boolean ok = true;
    for (int i = 0; i < n; i++) {
        if (polinom.get(i).getCoef().doubleValue() != 0) {
            ok = false;
            break;
        }
    }
    double numar = monom.getCoef().doubleValue();
    if (ok == true && numar > 0) {
        text = monom.toString();
    } else {
        text = "+" + monom.toString();
    }
    if (numar < 0) {// numarul are inclus semn negativ
        text = monom.toString();
    }
    return text;
}

如果我忘记了任何信息，请问我。

Answer 1

你正在打电话

verificare(polinom.get(polinom.size() - 1), polinom,' 'polinom.size() - 1);

并获得带有-1值的ArrayIndexOutOfBoundsException，表明当您收到错误时，您的polinom集合的大小为0。检查这一点，如果大小为0，则不要调用此方法。

Answer 2

在你的方法中：

public  Polinom toPolinom(String p1) {
    ....
    for(i=0; i<p1.length()-1; i=i+5){

你将每个循环增加约5

所以想象一下这个字符串＆＃34; 1234567＆＃34;：第一个循环你得到12345，下一循环只有67，但你试着这样做：

grad=Character.getNumericValue(p1.charAt(i+4));

此刻，i + 4 = 9，这是outOfBound ...... 我猜（没有测试过，你没有显示出错的行）这是你的问题

Answer 3

在我修改方法toString()和verificare()之后，一切都运行良好，如下所示：

      public String toString() {
    int ok = 0;
    String Rezultat = "";
    for (int i = 0; i < polinom.size(); i++) {
        Rezultat = Rezultat + verificare(polinom.get(i), polinom, i);
        if (polinom.get(i).getCoef().doubleValue() != 0)
            ok = 1;
    }
    if (ok == 1)
        return Rezultat;
    else
        return "0";

}

private String verificare(Monom monom, List<Monom> polinom, int n) {
    String text = "";

    double numar = monom.getCoef().doubleValue();
    if (n != 0 && numar > 0) {

        text = "+" + monom.toString();
    } else
        text = monom.toString();
    if (numar < 0) {// numarul are inclus semn negativ
        text = monom.toString();
    }
    return text;

}

非常感谢你的帮助！

Swing Java接口实现错误

3 个答案: