public static void main(String[] args){
        if(args.length != 1){
            System.out.println("please input a hex number");
            return;
        }
        try
        {
            int num = Integer.parseInt(args[0].substring(2), 16);
            System.out.println(num);
        }
        catch(Exception e){
        
            System.out.println("please input a correct hex number");
        }
    }

------解决方案--------------------
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Java codepublic static void main(String[] args){
        if(args.length != 1){
            System.out.println("please input a hex number");
            return;
        }
        try
        {
            int num = Integer.parseInt(args[0].substring(2), 16);
            System.out.println(num);
        }
        catch(Exception e){
        
            System.out.println("please input…


------解决方案--------------------
import java.awt.*;  
public class d2x extends Frame  
{  
int decimalValue= 0;  
String baseXValue = new String("0");  
TextField dDisplay,xDisplay;  
//d2x constructor  
d2x()  
{  
super("Decimal Converter");//set the title of the frame  
MenuBar mb = new MenuBar();  
Button d2Binary = new Button("Binary");  
Button d2Octal = new Button("Octal");  
Button d2Hex = new Button("Hex");  
Button d2Base36 = new Button("Base36");  
Panel p1 = new Panel();  
Panel p2 = new Panel();  
Panel p3 = new Panel();  

//add a simple menu  
Menu m = new Menu("Application");  
m.add(new CheckboxMenuItem("Base 36 Active"));  
m.add(new MenuItem("Exit"));  

//add menu to menubar  
mb.add(m);  
setMenuBar(mb);//install this menu bar in the frame  

//Add buttons to their own panel  
p3.setLayout(new FlowLayout());  
p3.add(d2Binary);  
p3.add(d2Octal);  
p3.add(d2Hex);  
p3.add(d2Base36);  

//Add text fields  
Label dLabel = new Label("Enter Deecimal: ");  
Label xLabel = new Label("Converted Value: ");  
dDisplay = new TextField(Integer.toString(decimalValue),7);  
xDisplay = new TextField(baseXValue,32);  
xDisplay.setEditable(false);  
p1.setLayout(new FlowLayout(FlowLayout.LEFT));  
p2.setLayout(new FlowLayout(FlowLayout.LEFT));  
p1.add(dLabel);  
p1.add(dDisplay);  
p2.add(xLabel);  
p2.add(xDisplay);  

//Add the panels  
add("North",p1);  
add("Center",p2);  
add("South",p3);  
}//end d2x constructor  

public void start()  
{  
resize(400,150);  
show();  
}  

public void updateXDisplay()  
{  
xDisplay.setText(baseXValue);  
}  

public boolean handleEvent(Event evt)  
{  
if (evt.target instanceof MenuItem)  
{  
if ("Exit".equals(((MenuItem)evt.target).getLabel()))  
{  
hide();  
dispose();  
System.exit(0);  
return false;  
}  
return true;