import java.text.*;
public class Date
{
    //类变量声明部分
    private int month;
    private int day;
    private int year;
    
    //类方法定义部分
    Date()
    {          //这是一个构造方法，因为它和类名相同
        month = 7;
        day = 4;
        year = 2001;
        System.out.println("From the default constructor:"+"\n Created a new date
            object with data values"+"\n month="+month+"day="+day+"year="+year);
           
    }
    Date(int mm,int dd,int yyyy)   //这是一个重载构造方法
    {
        month = mm;
        day = dd;
        year = yyyy;
        System.out.println("From the default constructor:"+"\n Created a new date  
            object with data values"+"\n month="+month+"day="+day+"year="+year);
           
    }
    Date(long yyyymmdd)    //第二个构造方法
    {
        year = int(yyyymmdd/10000.0);    //抽取年
        month = int((yyyymmdd - year*10000.0) / 100.0);
        day = int(yyyymmdd - year * 10000.0 - month*100.0);
        System.out.println("From the second overloaded constructor:"
           +"\n Created a new Date object with data values"
           +"\n month ="+ month +  "day="+day   "year="+year);
    }
    public void setDate(int mm,int dd,int yyyy)
    {
      month = mm;
      day = dd;
      year = yyyy;
    }
    public void showDate()
    {
      DecimalFormat df = new DecimalFormat("00");
      System.out.println("The date is" +df.format(month) +'/'+df.format(day)
                             + '/'+ df.format(year%100));  //精确到最后两位
    }
    {
      Date a = new Date ();    //声明一个Date类型的对象
      Date b = new Date (5,1,2004);
      Date c = new Date (20050915L);
    }
}

import java.text.*;
public class Date
{
    //类变量声明部分
    private int month;
    private int day;
    private int year;
   
    //类方法定义部分
    Date()
    {          //这是一个构造方法，因为它和类名相同
        month = 7;
        day = 4;
        year = 2001;
        System.out.println("From the default constructor:"+"\n Created a new date object with data values"+"\n month="+month+"day="+day+"year="+year);
           
    }
    Date(int mm,int dd,int yyyy)   //这是一个重载构造方法
    {
        month = mm;
        day = dd;
        year = yyyy;
        System.out.println("From the default constructor:"+"\n Created a new date object with data values"+"\n month="+month+"day="+day+"year="+year);
           
    }
    Date(long yyyymmdd)    //第二个构造方法
    {
        year = (int)(yyyymmdd/10000.0);    //抽取年
        month = (int)((yyyymmdd - year*10000.0) / 100.0);
        day = (int)(yyyymmdd - year * 10000.0 - month*100.0);
        System.out.println("From the second overloaded constructor:"
           +"\n Created a new Date object with data values"
           +"\n month ="+ month +  "day="+day  + "year="+year);
    }
    public void setDate(int mm,int dd,int yyyy)
    {
      month = mm;
      day = dd;
      year = yyyy;
    }
    public void showDate()
    {
      DecimalFormat df = new DecimalFormat("00");
      System.out.println("The date is" +df.format(month) +'/'+df.format(day)
                             + '/'+ df.format(year%100));  //精确到最后两位
    }
    {
     Datea = new Date ();    //声明一个Date类型的对象
      Date b = new Date (5,1,2004);
      Date c = new Date (20050915L);
    }
}

LZ，你的程序中有一些语法和格式有问题，比如数据转换中，year=(int)(yyyymmdd/10000.0)，int要加括号的。现在的可以编译了。