java - Java：按位与创建无符号字节

Question

我想创建一个位数组，它将通过串行 RS232 发送到 Arduino 以控制输出引脚。

I'm doing this by creating checkboxes which when selected send a byte which each bit referring to a pin (on or off).

我已经使用按位与操作实现了前 8 个复选框的代码，并打印到系统输出以确认我得到了正确的位模式。

它适用于前 7 个复选框，但第 8 个复选框不起作用，因为 java 字节已签名并且不允许我将 '255' 分配给字节值。有没有解决的办法？

重要的代码是这一点：

    private void createOutputChars(){
    byte outputByte1 = 0;
    byte testByte = 1;
    for (int x = 0;x < 8;x++){
        if (digitalPinOutputArray[x].isSelected()) {
           outputByte1 += (byte) (testByte);
        }
        testByte = (byte) (testByte << 1);
    }

    printByteArray(outputByte1);

}


private void printByteArray(int inputByte) {
    // print out 1 or 0
    byte comparison = 0x1;
    for (int x = 0;x < 8;x++)
    {
        if ((inputByte & comparison) > 0) {
            System.out.print("1");
        }
        else {System.out.print("0");}
        comparison = (byte) (comparison << 1);
    }
    System.out.println();
}

完整的可编译 Java 代码如下：

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package my.ArduinoGUI;


import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class ArduinoGUI extends javax.swing.JFrame {

/**
 * Creates new form ArduinoGUI
 */
public ArduinoGUI() {
    initCustomComponents();
    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.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

    buttonGroup1 = new javax.swing.ButtonGroup();
    jPanel1 = new javax.swing.JPanel();
    digitalPinPanel = new javax.swing.JPanel(new GridLayout(0, 3));
    jPanel3 = new javax.swing.JPanel(new GridLayout(0, 1));
    jPanel2 = new javax.swing.JPanel();
    jProgressBar1 = new javax.swing.JProgressBar();
    jProgressBar2 = new javax.swing.JProgressBar();
    jProgressBar3 = new javax.swing.JProgressBar();
    jProgressBar4 = new javax.swing.JProgressBar();
    jProgressBar5 = new javax.swing.JProgressBar();
    jProgressBar6 = new javax.swing.JProgressBar();
    jLabel1 = new javax.swing.JLabel();
    jLabel2 = new javax.swing.JLabel();
    jLabel3 = new javax.swing.JLabel();
    jLabel4 = new javax.swing.JLabel();
    jLabel5 = new javax.swing.JLabel();
    jLabel6 = new javax.swing.JLabel();
    jLabel7 = new javax.swing.JLabel();
    jLabel8 = new javax.swing.JLabel();
    jProgressBar7 = new javax.swing.JProgressBar();
    jProgressBar8 = new javax.swing.JProgressBar();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jPanel1.setBorder(javax.swing.BorderFactory.createTitledBorder("Outputs"));
    jPanel1.setName("Outputs"); // NOI18N

    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
    jPanel1.setLayout(jPanel1Layout);
    jPanel1Layout.setHorizontalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 209, Short.MAX_VALUE)
    );
    jPanel1Layout.setVerticalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 106, Short.MAX_VALUE)
    );

    digitalPinPanel.setBorder(javax.swing.BorderFactory.createTitledBorder("Digital Pin State"));
    digitalPinPanel.addMouseListener(new java.awt.event.MouseAdapter() {
        public void mouseReleased(java.awt.event.MouseEvent evt) {
            digitalPinPanelMouseReleased(evt);
        }
    });
    digitalPinLabelArray = new javax.swing.JLabel[digitalPinTotal];
    digitalPinRadioButtonArray = new javax.swing.JRadioButton[digitalPinTotal][2];
    digitalPinGroupArray = new javax.swing.ButtonGroup[digitalPinTotal];
    for(int x = 0; x < digitalPinTotal ; x++) {
        digitalPinGroupArray[x] = new javax.swing.ButtonGroup(); // populate button group
        digitalPinLabelArray[x] = new javax.swing.JLabel(); // populate label array
        digitalPinLabelArray[x].setText("Pin " + (x +2));
        digitalPinPanel.add(digitalPinLabelArray[x]); // add label to panel
        for(int y = 0; y < 2; y++){
            digitalPinRadioButtonArray[x][y] = new javax.swing.JRadioButton(); // populate radio button array
            digitalPinRadioButtonArray[x][y].addActionListener(new ActionListener() {

                public void actionPerformed(ActionEvent e)
                {
                    //Execute when button is pressed
                    System.out.println("You clicked the button");
                    checkOnOutputs();
                }
            }
        );

        if (y == 0) {digitalPinRadioButtonArray[x][y].setText("Input");}
        if (y == 1) {digitalPinRadioButtonArray[x][y].setText("Output"); digitalPinRadioButtonArray[x][y].setSelected(true);
        }

        digitalPinGroupArray[x].add(digitalPinRadioButtonArray[x][y]); // assign radio buttons to group
        digitalPinPanel.add(digitalPinRadioButtonArray[x][y]); // add buttons to panel
    }

}

jPanel3.setBorder(javax.swing.BorderFactory.createTitledBorder("Generated Boxes"));
digitalPinOutputArray = new javax.swing.JCheckBox[digitalPinTotal];

for(int x = 0; x < digitalPinTotal ; x++) {
    digitalPinOutputArray[x] = new javax.swing.JCheckBox();
    digitalPinOutputArray[x].setText("Output Pin " + (x+2));
    digitalPinOutputArray[x].addActionListener(new ActionListener() {

        public void actionPerformed(ActionEvent e)
        {
            //Execute when button is pressed
            createOutputChars();
        }
    });
    jPanel3.add(digitalPinOutputArray[x]);

}

jPanel2.setBorder(javax.swing.BorderFactory.createTitledBorder("Analog Pin State"));

jProgressBar1.setMaximum(1024);
jProgressBar1.setToolTipText("");
jProgressBar1.setString(Integer.toString(jProgressBar1.getValue()));
jProgressBar1.setStringPainted(true);

jProgressBar2.setMaximum(1024);
jProgressBar2.setString(Integer.toString(jProgressBar2.getValue()));
jProgressBar2.setStringPainted(true);

jProgressBar3.setMaximum(1024);
jProgressBar3.setString(Integer.toString(jProgressBar3.getValue()));
jProgressBar3.setStringPainted(true);

jProgressBar4.setMaximum(1024);
jProgressBar4.setString(Integer.toString(jProgressBar4.getValue()));
jProgressBar4.setStringPainted(true);

jProgressBar5.setMaximum(1024);
jProgressBar5.setString(Integer.toString(jProgressBar5.getValue()));
jProgressBar5.setStringPainted(true);

jProgressBar6.setMaximum(1024);
jProgressBar6.setString(Integer.toString(jProgressBar6.getValue()));
jProgressBar6.setStringPainted(true);

jLabel1.setText("Pin A0");

jLabel2.setText("Pin A1");

jLabel3.setText("Pin A6");

jLabel4.setText("Pin A7");

jLabel5.setText("Pin A3");

jLabel6.setText("Pin A2");

jLabel7.setText("Pin A4");

jLabel8.setText("Pin A5");

jProgressBar7.setMaximum(1024);
jProgressBar7.setToolTipText("");
jProgressBar7.setString(Integer.toString(jProgressBar7.getValue()));
jProgressBar7.setStringPainted(true);

jProgressBar8.setMaximum(1024);
jProgressBar8.setToolTipText("");
jProgressBar8.setString(Integer.toString(jProgressBar8.getValue()));
jProgressBar8.setStringPainted(true);

javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
jPanel2.setLayout(jPanel2Layout);
jPanel2Layout.setHorizontalGroup(
    jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
    .addGroup(jPanel2Layout.createSequentialGroup()
        .addContainerGap()
        .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jLabel7)
                    .addComponent(jProgressBar1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jProgressBar5, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jProgressBar6, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel1)
                    .addComponent(jLabel2)
                    .addComponent(jProgressBar2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel8)
                    .addComponent(jLabel5)
                    .addComponent(jLabel3)
                    .addComponent(jProgressBar7, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jProgressBar3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(18, Short.MAX_VALUE))
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jLabel6)
                    .addComponent(jProgressBar4, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel4)
                    .addComponent(jProgressBar8, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(0, 0, Short.MAX_VALUE))))
);
jPanel2Layout.setVerticalGroup(
    jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
    .addGroup(jPanel2Layout.createSequentialGroup()
        .addContainerGap()
        .addComponent(jLabel1)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jProgressBar1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addGap(4, 4, 4)
        .addComponent(jLabel2)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jProgressBar2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jLabel6)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
        .addComponent(jProgressBar3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jLabel5)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jProgressBar4, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jLabel7)
        .addGap(9, 9, 9)
        .addComponent(jProgressBar5, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jLabel8)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jProgressBar6, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jLabel3)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jProgressBar7, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jLabel4)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jProgressBar8, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addContainerGap(65, Short.MAX_VALUE))
);

javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
    layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
    .addGroup(layout.createSequentialGroup()
        .addContainerGap()
        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addComponent(jPanel3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
        .addGap(18, 18, 18)
        .addComponent(digitalPinPanel, javax.swing.GroupLayout.PREFERRED_SIZE, 159, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
        .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
        .addContainerGap(306, Short.MAX_VALUE))
);
layout.setVerticalGroup(
    layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
    .addGroup(layout.createSequentialGroup()
        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
            .addGroup(layout.createSequentialGroup()
                .addGap(23, 23, 23)
                .addComponent(jPanel3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGap(18, 18, 18)
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(digitalPinPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jPanel2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))))
        .addContainerGap())
);

digitalPinPanel.getAccessibleContext().setAccessibleName("");

pack();
}// </editor-fold>

private void digitalPinPanelMouseReleased(java.awt.event.MouseEvent evt) {                                              



}                                             

private void checkOnOutputs() {
    // if output selected enable checkbox otherwise disable it
    for (int x = 0; x < digitalPinTotal; x++) {

        if (digitalPinRadioButtonArray[x][0].isSelected() == true) {
            digitalPinOutputArray[x].setEnabled(false);
        }

        if (digitalPinRadioButtonArray[x][1].isSelected() == true) {
            digitalPinOutputArray[x].setEnabled(true);
        }

    }
}


/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Windows".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(ArduinoGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(ArduinoGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(ArduinoGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(ArduinoGUI.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new ArduinoGUI().setVisible(true);
        }
    });
}
// Variables declaration - do not modify
private javax.swing.ButtonGroup buttonGroup1;
private javax.swing.JPanel digitalPinPanel;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JLabel jLabel5;
private javax.swing.JLabel jLabel6;
private javax.swing.JLabel jLabel7;
private javax.swing.JLabel jLabel8;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JPanel jPanel3;
private javax.swing.JProgressBar jProgressBar1;
private javax.swing.JProgressBar jProgressBar2;
private javax.swing.JProgressBar jProgressBar3;
private javax.swing.JProgressBar jProgressBar4;
private javax.swing.JProgressBar jProgressBar5;
private javax.swing.JProgressBar jProgressBar6;
private javax.swing.JProgressBar jProgressBar7;
private javax.swing.JProgressBar jProgressBar8;
// End of variables declaration
private int digitalPinTotal = 12;
private int analogPinTotal = 8;
private javax.swing.JCheckBox[] digitalPinOutputArray;
private javax.swing.JRadioButton[][] digitalPinRadioButtonArray;
private javax.swing.ButtonGroup[] digitalPinGroupArray;
private javax.swing.JLabel[] digitalPinLabelArray;

private void initCustomComponents() {
    //throw new UnsupportedOperationException("Not yet implemented");
    // create checkbox array
}

private void createOutputChars(){
    byte outputByte1 = 0;
    byte testByte = 1;
    for (int x = 0;x < 8;x++){
        if (digitalPinOutputArray[x].isSelected()) {
           outputByte1 += (byte) (testByte);
        }
        testByte = (byte) (testByte << 1);
    }

    printByteArray(outputByte1);

}


private void printByteArray(int inputByte) {
    // print out 1 or 0
    byte comparison = 0x1;
    for (int x = 0;x < 8;x++)
    {
        if ((inputByte & comparison) > 0) {
            System.out.print("1");
        }
        else {System.out.print("0");}
        comparison = (byte) (comparison << 1);
    }
    System.out.println();
}

}

Answer 1

只需忽略 java 字节已签名的事实。它只对少数操作（最显着的关系运算符，如 >）产生影响。

位运算符 (|, & , ^) 提供与字节无符号时相同的位模式结果。

我只会将要控制的位数存储到组合框并像这样设置/读取位：

public static boolean isBitSet(byte b, int bitNo) {
    return (b & (1 << bitNo) != 0;
}

public static byte setBit(byte b, int bitNo) {
    return (byte) (b | (1 << bitNo));
}

public static byte clearBit(byte b, int bitNo) {
    return (byte) (b & (~(1 << bitNo)));
}

虽然由于缺少无符号类型，直接将 C 代码移植到 java 通常会导致不同的行为，但差异并不是那么大。所有无符号类型都可以替换为有符号类型，它只需要一些注意力（和知识），因为某些操作需要以不同的方式表达。

顺便说一句：没有人会如此耐心地挖掘由 UI 构建器生成的代码墙。如果您有具体问题，请提供一个简短的示例，最好是可编译和可执行的。

Answer 2

当您将字节用作 8 位值时，没有符号位。当您将字节用作数字时，它只是一个符号位。这是一个例子：

public class LearnByte
{
    public static void main(final String[] arguments)
    {
        byte hootBerry;

        hootBerry = 0x10;
        System.out.printf("0x%x\t%d\n", hootBerry, hootBerry);

        hootBerry |= 0x81;
        System.out.printf("0x%x\t%d\n", hootBerry, hootBerry);
    }
}