JAVA中根据以下代码将int数据转换为byte数据：
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public static byte[] int32ToBytes(int val) {
int size = Integer.SIZE / Byte.SIZE;
byte[] ret = new byte[size];
for (int i = 0; i size; ++i) {
ret[i] = (byte) (val (8 * i) 56);
}
return ret;
}
扩展资料
Java也提供了一个byte数据类型，并且是基本类型。java byte是做为最小的数字来处理的，因此它的值域被定义为-128~127，也就是signed byte。
byte，即字节，由8位的二进制组成。在Java中，byte类型的数据是8位带符号的二进制数。在计算机中，8位带符号二进制数的取值范围是[-128, 127]，所以在Java中，byte类型的取值范围也是[-128, 127]。
运算规则：
####正数的最高位都是 0 ，正数的值就是二进制表示的值。 ####
####负数的最高位都是 1 ，负数的值是 取反后加一 然后加个负号得到得值。 ####
1、创建java类，TestBigInteger.java；
2、编写java代码；
public class TestBigInteger {
public static void main(String[] args) {
BigInteger bint = new BigInteger(String.valueOf(123));
}
}
3、编写输出结果代码；
System.out.println(bint);
System.out.println(bint.getClass());
4、执行结果，类型为‘class java.math.BigInteger’；
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
public class UnitTransfer extends JFrame{
private final int WIDTH = 400, HEIGHT = 300;//窗口默认的宽度、高度
private JLabel lblInUnit=new JLabel("输入单位");
private JComboBox cboIn=new JComboBox(new String[]{"", ""});
private JLabel lblIn=new JLabel("输入数值");
private JTextField txtIn=new JTextField("10");
private JLabel lblOutUnit=new JLabel("输出单位");
private JLabel lblResult=new JLabel("显示结果");
private JLabel txtResult=new JLabel("结果");
private JComboBox cboOut=new JComboBox(new String[]{"", ""});
private JButton btnTrans = new JButton("转换");
private JButton btnClear = new JButton("清空");
private JRadioButton rdLeng = new JRadioButton("长度");
private JRadioButton rdWeig = new JRadioButton("时间");
private String [] lengthUnit={"米", "分米", "厘米", "毫米"};
private String [] timeUnit={"天", "时", "分", "秒"};
public UnitTransfer(){
super("简单的单位转换器 Beta");
this.setSize(WIDTH, HEIGHT);
this.setLayout(null);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
ButtonGroup group = new ButtonGroup();
group.add(rdLeng);
group.add(rdWeig);
this.getContentPane().add(rdLeng);
this.getContentPane().add(rdWeig);
this.getContentPane().add(btnTrans);
this.getContentPane().add(btnClear);
this.getContentPane().add(lblIn);
this.getContentPane().add(txtIn);
this.getContentPane().add(lblInUnit);
this.getContentPane().add(cboIn);
this.getContentPane().add(lblResult);
this.getContentPane().add(txtResult);
this.getContentPane().add(lblOutUnit);
this.getContentPane().add(cboOut);
this.setVisible(true);
this.doLayout();
btnTrans.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
doConvert();
}
});
btnClear.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
txtIn.setText("0");
txtResult.setText("0");
}
});
rdLeng.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
cboIn.setModel(new DefaultComboBoxModel(lengthUnit));
cboOut.setModel(new DefaultComboBoxModel(lengthUnit));
}
});
rdWeig.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
cboIn.setModel(new DefaultComboBoxModel(timeUnit));
cboOut.setModel(new DefaultComboBoxModel(timeUnit));
}
});
rdLeng.setSelected(true);
cboIn.setModel(new DefaultComboBoxModel(lengthUnit));
cboOut.setModel(new DefaultComboBoxModel(timeUnit));
}
final int offX=100;
public void doLayout(){
super.doLayout();
rdLeng.setBounds(offX, 15, 60, 20);
rdWeig.setBounds(rdLeng.getX()+rdLeng.getWidth()+5, 15, 60, 20);
lblInUnit.setBounds(offX, rdLeng.getY()+rdLeng.getHeight()+20, 80, 20);
cboIn.setBounds(lblInUnit.getX()+lblInUnit.getWidth()+5, lblInUnit.getY(), 80, 20);
lblIn.setBounds(offX, lblInUnit.getY()+lblInUnit.getHeight()+5, 80, 20);
txtIn.setBounds(lblIn.getX()+lblIn.getWidth()+5, lblIn.getY(), 80, 20);
lblOutUnit.setBounds(offX, lblIn.getY()+lblIn.getHeight()+30, 80, 20);
cboOut.setBounds(lblOutUnit.getX()+lblOutUnit.getWidth()+5, lblOutUnit.getY(), 80, 20);
lblResult.setBounds(offX, cboOut.getY()+cboOut.getHeight()+5, 80, 20);
txtResult.setBounds(lblResult.getX()+lblResult.getWidth()+5, lblResult.getY(), 100, 20);
int w=getWidth ();
int x=(w-70*2-5)/2;//水平居中
btnTrans.setBounds(x, lblResult.getY()+lblResult.getHeight()+30, 70, 25);
btnClear.setBounds(btnTrans.getX()+btnTrans.getWidth()+3, btnTrans.getY(), 70, 25);
}
public void doConvert(){
double v=0;
try{
v= Double.parseDouble(txtIn.getText());
}catch(Exception ex){
txtIn.setText("0");
return;
}
//"米", "分米", "厘米", "毫米"
if(rdLeng.isSelected()){
switch(cboIn.getSelectedIndex()){
case 0:
break;
case 1:
v=v/10;
break;
case 2:
v=v/100;
break;
case 3:
v=v/1000;
break;
default:
return;
}
//v 现在是标准单位：米
switch(cboOut.getSelectedIndex()){
case 0:
break;
case 1:
v=v*10;
break;
case 2:
v=v*100;
break;
case 3:
v=v*1000;
break;
default:
return;
}
if(v0.01){
txtResult.setText(String.format("%2.8f", v));
}else{
txtResult.setText(String.format("%2.2f", v));
}
}else{
//"天", "时", "分", "秒"
switch(cboIn.getSelectedIndex()){
case 0:
v=v*24;
break;
case 1:
break;
case 2:
v=v/60;
break;
case 3:
v=v/3600;
break;
default:
return;
}
//v 现在是标准单位：小时
switch(cboOut.getSelectedIndex()){
case 0:
v=v/24;
break;
case 1:
break;
case 2:
v=v*60;
break;
case 3:
v=v*3600;
break;
default:
return;
}
if(v0.01){
txtResult.setText(String.format("%2.8f", v));
}else{
txtResult.setText(String.format("%2.8f", v));
}
}
}
public static void main(String[] args){
EventQueue.invokeLater(new Runnable() {
public void run() {
new UnitTransfer();
}
});
}
}
//请参考，欢迎指正