corejava第8版

corejava第8版/v2ch01/RandomFileTest/RandomFileTest.java

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+import java.io.*;
+import java.util.*;
+
+/**
+ * @version 1.11 2004-05-11
+ * @author Cay Horstmann
+ */
+public class RandomFileTest
+{  
+   public static void main(String[] args)
+   {
+      Employee[] staff = new Employee[3];
+
+      staff[0] = new Employee("Carl Cracker", 75000, 1987, 12, 15);
+      staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
+      staff[2] = new Employee("Tony Tester", 40000, 1990, 3, 15);
+
+      try
+      {  
+         // save all employee records to the file employee.dat
+         DataOutputStream out = new DataOutputStream(new FileOutputStream("employee.dat"));
+         for (Employee e : staff)
+            e.writeData(out);
+         out.close();
+      
+         // retrieve all records into a new array
+         RandomAccessFile in = new RandomAccessFile("employee.dat", "r");   
+         // compute the array size
+         int n = (int)(in.length() / Employee.RECORD_SIZE);
+         Employee[] newStaff = new Employee[n];
+
+         // read employees in reverse order
+         for (int i = n - 1; i >= 0; i--)
+         {  
+            newStaff[i] = new Employee();
+            in.seek(i * Employee.RECORD_SIZE);
+            newStaff[i].readData(in);
+         }
+         in.close();
+         
+         // print the newly read employee records
+         for (Employee e : newStaff) 
+            System.out.println(e);
+      }
+      catch (IOException e)
+      {  
+         e.printStackTrace(); 
+      }
+   }
+}
+
+class Employee
+{
+   public Employee() {}
+
+   public Employee(String n, double s, int year, int month, int day)
+   {  
+      name = n;
+      salary = s;
+      GregorianCalendar calendar = new GregorianCalendar(year, month - 1, day);
+      hireDay = calendar.getTime();
+   }
+
+   public String getName()
+   {
+      return name;
+   }
+
+   public double getSalary()
+   {
+      return salary;
+   }
+
+   public Date getHireDay()
+   {  
+      return hireDay;
+   }
+
+   /**
+      Raises the salary of this employee.
+      @byPercent the percentage of the raise
+   */
+   public void raiseSalary(double byPercent)
+   {  
+      double raise = salary * byPercent / 100;
+      salary += raise;
+   }
+
+   public String toString()
+   {  
+      return getClass().getName()
+         + "[name=" + name
+         + ",salary=" + salary
+         + ",hireDay=" + hireDay
+         + "]";
+   }
+
+   /**
+      Writes employee data to a data output
+      @param out the data output
+   */
+   public void writeData(DataOutput out) throws IOException
+   {
+      DataIO.writeFixedString(name, NAME_SIZE, out);
+      out.writeDouble(salary);
+
+      GregorianCalendar calendar = new GregorianCalendar();
+      calendar.setTime(hireDay);
+      out.writeInt(calendar.get(Calendar.YEAR));
+      out.writeInt(calendar.get(Calendar.MONTH) + 1);
+      out.writeInt(calendar.get(Calendar.DAY_OF_MONTH));
+   }
+
+   /**
+      Reads employee data from a data input
+      @param in the data input
+   */
+   public void readData(DataInput in) throws IOException
+   {
+      name = DataIO.readFixedString(NAME_SIZE, in);
+      salary = in.readDouble();
+      int y = in.readInt();
+      int m = in.readInt();
+      int d = in.readInt();
+      GregorianCalendar calendar = new GregorianCalendar(y, m - 1, d);
+      hireDay = calendar.getTime();
+   }
+
+   public static final int NAME_SIZE = 40;
+   public static final int RECORD_SIZE = 2 * NAME_SIZE + 8 + 4 + 4 + 4;
+
+   private String name;
+   private double salary;
+   private Date hireDay;
+}
+
+class DataIO
+{
+   public static String readFixedString(int size, DataInput in) 
+      throws IOException
+   {  
+      StringBuilder b = new StringBuilder(size);
+      int i = 0;
+      boolean more = true;
+      while (more && i < size)
+      {  
+         char ch = in.readChar();
+         i++;
+         if (ch == 0) more = false;
+         else b.append(ch);
+      }
+      in.skipBytes(2 * (size - i));
+      return b.toString();
+   }
+
+   public static void writeFixedString(String s, int size, DataOutput out) 
+      throws IOException
+   {
+      for (int i = 0; i < size; i++)
+      {  
+         char ch = 0;
+         if (i < s.length()) ch = s.charAt(i);
+         out.writeChar(ch);
+      }
+   }
+}