arraysorttest.java

一些Java写的测试API的源代码

/*
在Java中，所有的数组都有一个缺省的属性length,用于获取数组中元素的个数
数组的复制：　System.arraycopy();
数组的排序:   Arrays.sort();
在已排序的数组中查找某个元素：	Arrays.binarySearch();

*/
import java.util.Arrays;

class ArraySortTest
{
	public static void main(String[] args)
	{
		/*
		int[] num = new int[]{3,1,2};
		Arrays.sort(num);		
		for (int i=0;i<num.length;i++)
		{
			System.out.println(num[i]);
		}
		
		int index = Arrays.binarySearch(num,3);
		System.out.println("index= "+index);
		System.out.println("element="+num[index]);
		*/
		
		
		/*Sort 
		 *public static void sort(Object[] a)
		 *
		 * Sorts the specified array of objects into ascending order,according to 
		 *the natural ordering of its elements.All elements in the array must 
		 *implements the Comparable interface.Furthermore,all elements in the 
		 *array must be mutually comparable(that is,e1.compareTo(e2)must not throw
		 *a ClassCastException for any elements e1 and e2 int the array).
		 *
		 *
		 *
		 **/
		 
		/*　对于自定义的对象数组排序功能实现
		 *用Arrays.sort(对象数组);时
		 *必须对使自定义的对象实现Comparable接口
		 *实现Comparable接口中的compareTo方法
		 *关于些方法见JDK－API;
		 *　*/
		Student[] ss =new Student[]{new Student("miracle",20),
									new Student("djb",21),
									new Student("deng",19),
									new Student("ajb",21)};
		Arrays.sort(ss);
		for (int i=0;i<ss.length;i++)
		{
			System.out.println(ss[i]);
		}
		
	}
}

class Student implements Comparable 
{
	int num;
	String name;
	Student(String name,int num)
	{
		this.num = num;
		this.name = name;	
	}
	public String toString()
	{
		return "number="+num+","+"name="+name;
		
	}
	
	public int compareTo(Object o)
	{	
		Student s = (Student)o;
		//return num>s.num?1:(num==s.num?0:-1);
		int result = num>s.num?1:(num==s.num?0:-1);
		if(0 == result)
		{
			/*　String类中已经实现了Comparable接口中的compareTo方法
			 *可以直接使用。
			 **/
			result = name.compareTo(s.name);
		}
		return result;
	}
}