java之路，数组

java中所有的数组都有一个缺省的属性length，用于获取数组元素的个数
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()
arraycopy(
        Object src,                  //源数组
         int      srcPos,             //拷贝位置
        Object dest,               //目的数组
        int       desPos,           //目的位置
        int length                  //长度
)

class ArrayTest
{
    public static void main(String[] args)
    {
        int[] num1 = new int[]{4,2,3};
        int[] num2 = new int[3];
        System.arraycopy(num1, 0, num2, 0, num1.length);            //复制数组
        Arrays.sort(num1);                //排序，升序，需要引入java.util包
        int index = Arrays.binarySearch(num1,2);     //搜索的对应元素的序号

        for(int i=0; i             System.out.println(num2[2]);

        Point[] p1 = new Point[]{new Point(1,1), new Point(2,2), new Point(3,3) };
        Point[] p2 = new Point[3];
        System.arraycopy(p1, 0, p2, 0, p1.length);          //复制类数组
        p2[1].x = 100;
        p2[1].y = 100;
        System.out.println(p1[1].x + p1[1].y)          //p1也被修改了，因为类复制的时候，拷贝的是引用，也就是说拷贝的是地址

        Student ss = new Studen[]{new Student(1, "zs'),   new Student(2, "ls"), new Student(3, "ww")};
        Arrays.sort(ss);
        int index = Arrays.binarySearch(ss new Student(2, "lisi"));       //搜索必须在排序之后进行
   }
}

class Point
{
    int x,y;
    Point(int x, int y)
    {
        this.x = x;
        this.y = y;
    }
}
class Student implements Comparable        //类排序，需要实现Comparable方法
{
    int age;
    String name ;
    Student(int age, String name)
    {
         this.age = age;
         this.name = name;
    }
    public String toString()
   {
         return "age = " + age + "name = " +name;
    }
    public int compareTo(Object o)             // 自己实现排序，实现compareTo方法
     {
          Student s = (Student)o;
    //      return age > s.age ？ 1 : (age == s.age ? 0 : -1);             //按照年龄实现排序
          result = age > s.age ? 1: (age == s.age ? 0 : -1);
         if(result == 0)
         {
              result = name.compareTo(s.name);
         }
        return  result;

     }
}