corejava第10版

corejava第10版/v1ch04/StaticTest/StaticTest.java

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+/**
+ * This program demonstrates static methods.
+ * @version 1.01 2004-02-19
+ * @author Cay Horstmann
+ */
+public class StaticTest
+{
+   public static void main(String[] args)
+   {
+      // fill the staff array with three Employee objects
+      Employee[] staff = new Employee[3];
+
+      staff[0] = new Employee("Tom", 40000);
+      staff[1] = new Employee("Dick", 60000);
+      staff[2] = new Employee("Harry", 65000);
+
+      // print out information about all Employee objects
+      for (Employee e : staff)
+      {
+         e.setId();
+         System.out.println("name=" + e.getName() + ",id=" + e.getId() + ",salary="
+               + e.getSalary());
+      }
+
+      int n = Employee.getNextId(); // calls static method
+      System.out.println("Next available id=" + n);
+   }
+}
+
+class Employee
+{
+   private static int nextId = 1;
+
+   private String name;
+   private double salary;
+   private int id;
+
+   public Employee(String n, double s)
+   {
+      name = n;
+      salary = s;
+      id = 0;
+   }
+
+   public String getName()
+   {
+      return name;
+   }
+
+   public double getSalary()
+   {
+      return salary;
+   }
+
+   public int getId()
+   {
+      return id;
+   }
+
+   public void setId()
+   {
+      id = nextId; // set id to next available id
+      nextId++;
+   }
+
+   public static int getNextId()
+   {
+      return nextId; // returns static field
+   }
+
+   public static void main(String[] args) // unit test
+   {
+      Employee e = new Employee("Harry", 50000);
+      System.out.println(e.getName() + " " + e.getSalary());
+   }
+}