java杂记——数组拷贝

package javaBase16Lesson;

import java.util.Arrays;

/**
 * （1）
 *     int [] a = {1,2,3,4,5,6};
 *    int [] b = Arrays.copyOf(a, 8);    //把a拷贝到长度为8的b中。b的长度可比a长，长的部分补0；可比a短，把a截断。
 *    int [] c = Arrays.copyOfRange(a, 2, 5);  //把a的数组下标为2的到下标为5的前一个，拷贝到c中，c的长度为5-2=3。
 *
 *（2）
 *    int [] a = {1,2,3,4,5,6};
 *    int [] b = new int[8];
 *    System.arraycopy(a, 2, b, 3, 4);  //把数组a从下标为2的元素开始，拷贝长度为4的元素到b中，从b的下标为3的位置开始放。
 *                                                     //如果b的位置不足以放下指定长度的元素，会报java.lang.ArrayIndexOutOfBoundsException异常
 *
 *（3）
 *方法（1）（2）都只是数组的浅拷贝，无法实现深度拷贝
 * @author cnx
 * @Description : arrayCopyTest
 * @CreateDate ; 2014年7月9日 下午6:43:26
 */
public class Lesson9_arrayCopyTest {
    public static void main(String[] args) {
//        Lesson9_arrayCopyTest.arraysCopyOf();
//        Lesson9_arrayCopyTest.systemArraycopy();
        Lesson9_arrayCopyTest.deepArrayCopy();
    }
    
    
    public static void arraysCopyOf(){
        int [] a = {1,2,3,4,5,6};
        int [] b = Arrays.copyOf(a, 8);    //把a拷贝到长度为8的b中。b的长度可比a长，长的部分补0；可比a短，把a截断。
        int [] c = Arrays.copyOfRange(a, 2, 5);  //把a的数组下标为2的到下标为5的前一个，拷贝到c中，c的长度为5-2=3。
        System.out.println("a:"+ a.length);
        for (int i = 0; i < a.length; i++) {
            System.out.println(a[i]);
        }
        System.out.println("b:"+ b.length);
        for (int i : b) {
            System.out.println(i);
        }
        System.out.println("c:"+ c.length);
        for (int i : c) {
            System.out.println(i);
        }
    }
    /**
     *         Copies an array from the specified source array, beginning at the specified position, 
     * to the specified position of the destination array. A subsequence of array components 
     * are copied from the source array referenced by src to the destination array referenced by dest. 
     * The number of components copied is equal to the length argument. The components at positions 
     * srcPos through srcPos+length-1 in the source array are copied into positions destPos through 
     * destPos+length-1, respectively, of the destination array. 
     *         If the src and dest arguments refer to the same array object, then the copying is performed 
     * as if the components at positions srcPos through srcPos+length-1 were first copied to a temporary 
     * array with length components and then the contents of the temporary array were copied into 
     * positions destPos through destPos+length-1 of the destination array. <br>
     * 如果目标数组和源数组相同，则先拷贝到一个temp数组中，再从temp数组中拷回目标数组（源）
     */
    public static void systemArraycopy(){
        int [] a = {1,2,3,4,5,6};
        int [] b = new int[8];
        System.arraycopy(a, 2, b, 3, 4);  //把数组a从下标为2的元素开始，拷贝长度为4的元素到b中，从b的下标为3的位置开始放。
                                                         //如果b的位置不足以放下指定长度的元素，会报java.lang.ArrayIndexOutOfBoundsException异常
        System.out.println("a:"+ a.length);
        for (int i = 0; i < a.length; i++) {
            System.out.println(a[i]);
        }
        System.out.println("b:"+ b.length);
        for (int i : b) {
            System.out.println(i);
        }
    }
    
    /**
     * 上面的两种方法都无法实现深度拷贝
     */
    public static void deepArrayCopy(){
        Lesson9_array1 [] a1 = {new Lesson9_array1(),new Lesson9_array1()}; 
        Lesson9_array1 [] a2 = null;
        Lesson9_array1 [] a3 = new Lesson9_array1[3];
        Lesson9_array2 [] b1 = {new Lesson9_array2(),new Lesson9_array2()}; 
        Lesson9_array2 [] b2 = null;
        
        
        a2 = Arrays.copyOf(a1, 3);
        System.arraycopy(a1, 0, a3, 0, 2);
        b2 = Arrays.copyOf(b1, 3);
        
        a1[1].a = "a1";
        System.out.println(a2[1].a);
        System.out.println(a3[1].a);
        b1[1].a = "b1";
        System.out.println(b2[1].a);
    }
}


class Lesson9_array1 implements Cloneable{
    public String a = "deep";
    
    public Object clone(){
        Object o = null;
        try {
            o = (Lesson9_array1)super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return o;
    }
    
    public String toString(){
        return a;
    }
}

class Lesson9_array2{
    public String a = "deep";
    
    public String toString(){
        return a;
    }
}