即使条件变为false，也会在块内运行代码

时间：2014-01-09 06:24:41

标签： java

我不知道发生了什么。即使条件为false，如果块正在运行，代码也在内部。我在netbeans ide 7.4中设计了我的界面，只是在eclipse中复制粘贴设计。这是我的代码

import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class AddSymbol extends javax.swing.JFrame {

    /**
     * Creates new form NewJFrame
     */
    Connection c;
    public AddSymbol() {


        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */

    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {
        String x = "hello";
        if(x.equals("hii"))
        {
            System.out.println("Inside hi");
        }

        jinstrument = new javax.swing.JComboBox();
        jsymbol = new javax.swing.JComboBox();
        jexpiry = new javax.swing.JComboBox();
        joption = new javax.swing.JComboBox();
        jstrikeprice = new javax.swing.JComboBox();
        instrument = new javax.swing.JLabel();
        symbol = new javax.swing.JLabel();
        expiry = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jLabel5 = new javax.swing.JLabel();
        jPanel2 = new javax.swing.JPanel();
        instrumentLabel = new javax.swing.JLabel();
        symbolLabel = new javax.swing.JLabel();
        expiryLabel = new javax.swing.JLabel();
        optionLabel = new javax.swing.JLabel();
        strikeLabel = new javax.swing.JLabel();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        getContentPane().setLayout(null);

        jinstrument.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Equity", "OPTIDX", "OPTSTK", "FUTIDX", "FUTSTK", " " }));
        getContentPane().add(jinstrument);
        jinstrument.setBounds(10, 38, 83, 20);

        jsymbol.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
        getContentPane().add(jsymbol);
        jsymbol.setBounds(120, 38, 210, 20);

        jexpiry.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
        getContentPane().add(jexpiry);
        jexpiry.setBounds(380, 38, 180, 20);

        joption.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "PE", "CE" }));
        getContentPane().add(joption);
        joption.setBounds(10, 85, 66, 20);

        jstrikeprice.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
        getContentPane().add(jstrikeprice);
        jstrikeprice.setBounds(120, 85, 56, 20);

        instrument.setText("Instrument");
        getContentPane().add(instrument);
        instrument.setBounds(10, 13, 83, 14);

        symbol.setText("Symbol");
        getContentPane().add(symbol);
        symbol.setBounds(120, 13, 218, 14);

        expiry.setText("Expiry");
        getContentPane().add(expiry);
        expiry.setBounds(380, 13, 180, 14);

        jLabel4.setText("Option Type");
        getContentPane().add(jLabel4);
        jLabel4.setBounds(10, 69, 83, 14);

        jLabel5.setText("Strike Price");
        getContentPane().add(jLabel5);
        jLabel5.setBounds(120, 69, 56, 14);

        jPanel2.setLayout(null);

        jinstrument.addItemListener(new ItemListener() {

            @Override
            public void itemStateChanged(ItemEvent arg0) {
                // TODO Auto-generated method stub
                jsymbol.removeAllItems();
                int enterloop=0;
                if(jinstrument.getSelectedItem().equals("FUTSTK"))
                {
                    enterloop =1;
                }


                if(enterloop == 1);
                {   System.out.println("inside if");

                }

            }
        });



        getContentPane().add(jPanel2);
        jPanel2.setBounds(10, 135, 577, 338);


    }// </editor-fold>                        

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {

        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new AddSymbol().setVisible(true);
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JLabel expiry;
    private javax.swing.JLabel expiryLabel;
    private javax.swing.JLabel instrument;
    private javax.swing.JLabel instrumentLabel;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel5;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JComboBox jexpiry;
    private javax.swing.JComboBox jinstrument;
    private javax.swing.JComboBox joption;
    private javax.swing.JComboBox jstrikeprice;
    private javax.swing.JComboBox jsymbol;
    private javax.swing.JLabel optionLabel;
    private javax.swing.JLabel strikeLabel;
    private javax.swing.JLabel symbol;
    private javax.swing.JLabel symbolLabel;
    // End of variables declaration                   
}

无论我在jinstrument jcombobox中选择什么，我得到“内部if”作为输出。我已经检查了print语句但是enterloop的值为0并且它仍然进入if语句块。请帮我解决这个问题

4 个答案:

答案 0 :(得分：6)

此行;

中有一个if(enterloop == 1);

;表示语句结束。甚至if语句返回false，因此下一行将被执行

答案 1 :(得分：2)

删除第semicolon [;]行中的if(enterloop == 1);

答案 2 :(得分：0)

尝试这些更新的代码:: 

  import java.awt.event.ItemEvent;
  import java.awt.event.ItemListener;
  import java.sql.Connection;
  import java.sql.DriverManager;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.sql.Statement;

public class AddSymbol extends javax.swing.JFrame {

/**
 * Creates new form NewJFrame
 */
Connection c;
public AddSymbol() {


    initComponents();
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */

// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {
    String x = "hello";
    if(x.equals("hii"))
    {
        System.out.println("Inside hi");
    }

    jinstrument = new javax.swing.JComboBox();
    jsymbol = new javax.swing.JComboBox();
    jexpiry = new javax.swing.JComboBox();
    joption = new javax.swing.JComboBox();
    jstrikeprice = new javax.swing.JComboBox();
    instrument = new javax.swing.JLabel();
    symbol = new javax.swing.JLabel();
    expiry = new javax.swing.JLabel();
    jLabel4 = new javax.swing.JLabel();
    jLabel5 = new javax.swing.JLabel();
    jPanel2 = new javax.swing.JPanel();
    instrumentLabel = new javax.swing.JLabel();
    symbolLabel = new javax.swing.JLabel();
    expiryLabel = new javax.swing.JLabel();
    optionLabel = new javax.swing.JLabel();
    strikeLabel = new javax.swing.JLabel();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    getContentPane().setLayout(null);

    jinstrument.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Equity", "OPTIDX", "OPTSTK", "FUTIDX", "FUTSTK", " " }));
    getContentPane().add(jinstrument);
    jinstrument.setBounds(10, 38, 83, 20);

    jsymbol.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
    getContentPane().add(jsymbol);
    jsymbol.setBounds(120, 38, 210, 20);

    jexpiry.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
    getContentPane().add(jexpiry);
    jexpiry.setBounds(380, 38, 180, 20);

    joption.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "PE", "CE" }));
    getContentPane().add(joption);
    joption.setBounds(10, 85, 66, 20);

    jstrikeprice.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4" }));
    getContentPane().add(jstrikeprice);
    jstrikeprice.setBounds(120, 85, 56, 20);

    instrument.setText("Instrument");
    getContentPane().add(instrument);
    instrument.setBounds(10, 13, 83, 14);

    symbol.setText("Symbol");
    getContentPane().add(symbol);
    symbol.setBounds(120, 13, 218, 14);

    expiry.setText("Expiry");
    getContentPane().add(expiry);
    expiry.setBounds(380, 13, 180, 14);

    jLabel4.setText("Option Type");
    getContentPane().add(jLabel4);
    jLabel4.setBounds(10, 69, 83, 14);

    jLabel5.setText("Strike Price");
    getContentPane().add(jLabel5);
    jLabel5.setBounds(120, 69, 56, 14);

    jPanel2.setLayout(null);

    jinstrument.addItemListener(new ItemListener() {

        @Override
        public void itemStateChanged(ItemEvent arg0) {
            // TODO Auto-generated method stub
            jsymbol.removeAllItems();
            int enterloop=0;
            if(jinstrument.getSelectedItem().equals("FUTSTK"))
            {
                enterloop =1;
            }


            if(enterloop == 1);
            {   System.out.println("inside if")

            }

        }
    });

    instrumentLabel.setText("Instrument");
    jPanel2.add(instrumentLabel);
    instrumentLabel.setBounds(21, 11, 102, 14);

    symbolLabel.setText("Symbol");
    jPanel2.add(symbolLabel);
    symbolLabel.setBounds(129, 11, 126, 14);

    expiryLabel.setText("Expiry");
    jPanel2.add(expiryLabel);
    expiryLabel.setBounds(261, 11, 64, 14);

    optionLabel.setText("OptionType");
    jPanel2.add(optionLabel);
    optionLabel.setBounds(377, 11, 56, 14);

    strikeLabel.setText("Strike Price");
    jPanel2.add(strikeLabel);
    strikeLabel.setBounds(462, 11, 53, 14);

    getContentPane().add(jPanel2);
    jPanel2.setBounds(10, 135, 577, 338);


}// </editor-fold>                        

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {

    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new AddSymbol().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JLabel expiry;
private javax.swing.JLabel expiryLabel;
private javax.swing.JLabel instrument;
private javax.swing.JLabel instrumentLabel;
private javax.swing.JLabel jLabel4;
private javax.swing.JLabel jLabel5;
private javax.swing.JPanel jPanel2;
private javax.swing.JComboBox jexpiry;
private javax.swing.JComboBox jinstrument;
private javax.swing.JComboBox joption;
private javax.swing.JComboBox jstrikeprice;
private javax.swing.JComboBox jsymbol;
private javax.swing.JLabel optionLabel;
private javax.swing.JLabel strikeLabel;
private javax.swing.JLabel symbol;
private javax.swing.JLabel symbolLabel;
// End of variables declaration                   
 }

您的代码出错，因为您有“;”如

            if(enterloop == 1);
            {   System.out.println("inside if")

            }

在if条件之后不应该终止。 如果在你的条件之后有一个分号（终止），那么你在{//花括号}内写的任何代码将永远不会被执行。

答案 3 :(得分：0)

您的代码存在致命缺陷，即一个

if(enterloop == 1)    // ; bad semi-colon. Which, made this a single line if.
{                     // And, as a result this was "just" an anonymous code block.
  System.out.println("inside if");
}
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