java中的for each循环

可以用来依次处理数组中的每个元素(其他类型的元素集合亦可)而不必为指定下标值而分心。

这种for循环的语句格式为：

for(variable:collection) statement

定义一个变量用于暂存集合中的每一个元素，并执行相应的语句或者语句块。集合表达式必须是一个数组或者是一个实现了iterable接口的类对象，比如arrayList。

例如：

for(int element:a)

     Systm.out.println(element);

打印数组a的每一个元素，一个元素占一行。

如果不希望遍历整个集合，或者在循环内部需要操作下标值就需要使用传统的for循环。

1 import java.util.*;
 2 
 3 /**
 4  * This program tests the Employee class.
 5  * @version 1.11 2004-02-19
 6  * @author Cay Horstmann
 7  */
 8 public class EmployeeTest
 9 {
10    public static void main(String[] args)
11    {
12       // fill the staff array with three Employee objects
13       Employee[] staff = new Employee[3];
14 
15       staff[0] = new Employee("Carl Cracker", 75000, 1987, 12, 15);
16       staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
17       staff[2] = new Employee("Tony Tester", 40000, 1990, 3, 15);
18 
19       // raise everyone's salary by 5%
20       for (Employee e : staff)
21          e.raiseSalary(5);
22 
23       // print out information about all Employee objects
24       for (Employee e : staff)
25          System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay="
26                + e.getHireDay());
27    }
28 }
29 
30 class Employee
31 {
32    public Employee(String n, double s, int year, int month, int day)
33    {
34       name = n;
35       salary = s;
36       GregorianCalendar calendar = new GregorianCalendar(year, month - 1, day);
37       // GregorianCalendar uses 0 for January
38       hireDay = calendar.getTime();
39    }
40 
41    public String getName()
42    {
43       return name;
44    }
45 
46    public double getSalary()
47    {
48       return salary;
49    }
50 
51    public Date getHireDay()
52    {
53       return hireDay;
54    }
55 
56    public void raiseSalary(double byPercent)
57    {
58       double raise = salary * byPercent / 100;
59       salary += raise;
60    }
61 
62    private String name;
63    private double salary;
64    private Date hireDay;
65 }