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 }
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