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 objects13       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 objects24       for (Employee e : staff)25          System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay="26                + e.getHireDay());27    }28 }29 30 class Employee31 {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 January38       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 }