Array和Collection相互转换以及copy深度的小测

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    周末闲来无事，把java中Array和Collection之间相互转换小结了下，顺便对转换过程中涉及到的javabena的copy深度进行了简单的测试，详细内容将按照如下分类分别介绍：

• List <-> Array
• Set <-> Array
• List <-> Set
• List <-> Collection
• Array Copy
• List Copy

完整的代码：CollectionConvertTest.zip
测试过程中用到的javabean：TestVo的代码就不贴了，就一个简单的String属性name.

【一】、 List <-> Array

 System.out.println("==============================");

        // List -> Array
        System.out.println("List -> Array ");
        List<String> srclist = new ArrayList<String>();
        srclist.add("src_list_a");
        srclist.add("src_list_b");

        String[] destArr = srclist.toArray(new String[srclist.size()]);
        System.out.println("List -> Array 集合中元素的顺序不变");
        srclist.clear();
        System.out.println("srclist clear()");
        System.out.println("destArr length=" + destArr.length);
        if (destArr.length == 2) {
            System.out.println("List -> Array for String : 深度copy");
        } else {
            System.out.println("List -> Array for String : 浅度copy");
        }

        List<TestVo> srcVolist = new ArrayList<TestVo>();
        TestVo vo1 = new TestVo("michael");
        srcVolist.add(vo1);
        srcVolist.add(new TestVo("xiaoxiao"));
        srcVolist.add(new TestVo("vo_3"));

        TestVo[] destVoArr = srcVolist.toArray(new TestVo[srcVolist.size()]);
        System.out.println("List -> Array 集合中元素的顺序不变");
        vo1.setName("xiaoxiao_new");
        System.out.println("srcVolist[0]的属性Name修改为：xiaoxiao_new");
        System.out.println("destVoArr[0]的属性Name当前值：" + destVoArr[0].getName());
        if ("xiaoxiao_new".equals(destVoArr[0].getName())) {
            System.out.println("List -> Array for Bean : 浅度copy");
        } else {
            System.out.println("List -> Array for Bean : 深度copy");
        }

        // Array -> List
        System.out.println("Array -> List");
        String[] srcArr = new String[] { "src_arr_1", "src_arr_2" };
        List<String> destList = Arrays.asList(srcArr);
        srcArr[0] = "src_arr_1_new";
        if ("src_arr_1_new".equals(destList.get(0))) {
            System.out.println("Array -> List for String : 深度copy");
        } else {
            System.out.println("Array -> List for String : 浅度copy");
        }

        TestVo vo3 = new TestVo("vo_3");
        TestVo[] srcObjArr = new TestVo[] { vo3, new TestVo("vo_4") };

        List<TestVo> destObjList = Arrays.asList(srcObjArr);
        vo3.setName("vo_3_new");
        System.out.println(" srcObjArr[0]的属性Name修改为：vo_3_new");
        System.out.println("destObjList[0]的属性Name当前值："
                + destObjList.get(0).getName());
        if ("vo_3_new".equals(destObjList.get(0).getName())) {
            System.out.println("Array -> List for Bean : 浅度copy");
        } else {
            System.out.println("Array -> List for Bean : 深度copy");
        }
        System.out.println("==============================");

运行结果：

引用

==============================
List -> Array
List -> Array 集合中元素的顺序不变
srclist clear()
destArr length=2
List -> Array for String : 深度copy
List -> Array 集合中元素的顺序不变
srcVolist[0]的属性Name修改为：xiaoxiao_new
destVoArr[0]的属性Name当前值：xiaoxiao_new
List -> Array for Bean : 浅度copy
Array -> List
Array -> List for String : 深度copy
srcObjArr[0]的属性Name修改为：vo_3_new
destObjList[0]的属性Name当前值：vo_3_new
Array -> List for Bean : 浅度copy
==============================

【二】、 Set <-> Array

 System.out.println("==============================");
        // Set -> Array
        System.out.println("Set -> Array");
        System.out.println("Set -> Array 集合中元素的顺序会变");
        Set<String> srcSet = new HashSet<String>();
        srcSet.add("michael");
        srcSet.add("xiaoxiao");
        String[] destArr = srcSet.toArray(new String[srcSet.size()]);
        System.out.println(" String destArr size: " + destArr.length);

        Set<TestVo> srcObjSet = new HashSet<TestVo>();
        TestVo vo1 = new TestVo("michael");
        srcObjSet.add(vo1);
        srcObjSet.add(new TestVo("xiaoxiao"));

        TestVo[] destObjArr = srcObjSet.toArray(new TestVo[srcObjSet.size()]);
        vo1.setName("michael_new");
        System.out.println(" Bean destArr size: " + destArr.length);
        boolean deepFlag = true;
        for (TestVo vo : destObjArr) {
            if ("michael_new".equals(vo.getName())) {
                deepFlag = false;
                break;
            }
        }
        if (deepFlag) {
            System.out.println("Set -> Array for Bean : 深度copy");
        } else {
            System.out.println("Set -> Array for Bean : 浅度copy");
        }

        // Array -> Set
        System.out.println("Array -> Set");
        System.out.println("Array -> Set 集合中元素的顺序会变");
        String[] srcArr = new String[] { "michael", "xiaoxiao" };
        Set<String> destSet = new HashSet<String>(Arrays.asList(srcArr));

        System.out.println(" String destSet size: " + destSet.size());

        TestVo vo3 = new TestVo("michael");
        TestVo[] srcObjArr = new TestVo[] { vo1, new TestVo("xiaoxiao") };

        Set<TestVo> destObjSet = new HashSet<TestVo>(Arrays.asList(srcObjArr));
        vo3.setName("michael_new");
        System.out.println(" Bean dest Set size: " + destObjSet.size());
        deepFlag = true;
        for (TestVo vo : destObjSet) {
            if ("michael_new".equals(vo.getName())) {
                deepFlag = false;
                break;
            }
        }
        if (deepFlag) {
            System.out.println("Array -> Set for Bean : 深度copy");
        } else {
            System.out.println("Array -> Set for Bean : 浅度copy");
        }

        System.out.println("==============================");

执行结果：

引用

==============================
Set -> Array
Set -> Array 集合中元素的顺序会变
String destArr size: 2
Bean destArr size: 2
Set -> Array for Bean : 浅度copy
Array -> Set
Array -> Set 集合中元素的顺序会变
String destSet size: 2
Bean dest Set size: 2
Array -> Set for Bean : 浅度copy
==============================

【三】、 List <-> Set

System.out.println("==============================");
        // List -> Set
        System.out.println("List -> Set");
        System.out.println("List -> Set 集合中元素的顺序不变");
        List<String> srclist = new ArrayList<String>();
        srclist.add("src_list_a");
        srclist.add("src_list_b");

        Set<String> destSet = new HashSet<String>(srclist);
        srclist.clear();
        if (destSet.size() == 2) {
            System.out.println("List -> Set for String : 深度copy");
        } else {
            System.out.println("List -> Set for String : 浅度copy");
        }

        List<TestVo> srcObjList = new ArrayList<TestVo>();
        TestVo vo1 = new TestVo("michael");
        srcObjList.add(vo1);
        srcObjList.add(new TestVo("xiaoxiao"));

        Set<TestVo> destObjectSet = new HashSet<TestVo>(srcObjList);
        vo1.setName("michael_new");

        if ("michael_new".equals(destObjectSet.iterator().next().getName())) {
            System.out.println("List -> Set for Bean : 浅度copy");
        } else {
            System.out.println("List -> Set for Bean : 深度copy");
        }

        // Set -> List
        System.out.println("Set -> List");
        System.out.println("List -> Set 集合中元素的顺序会变");
        Set<String> srcSet = new HashSet<String>();
        srcSet.add("src_set_a");
        srcSet.add("src_set_b");
        List<String> destList = new ArrayList<String>(srcSet);
        srcSet.clear();
        if (destList.size() == 2) {
            System.out.println("Set -> List for String : 深度copy");
        } else {
            System.out.println("Set -> List for String : 浅度copy");
        }

        Set<TestVo> srcObjSet = new HashSet<TestVo>();
        TestVo vo3 = new TestVo("vo_3");
        srcObjSet.add(vo3);
        srcObjSet.add(new TestVo("vo_4"));

        List<TestVo> destObjList = new ArrayList<TestVo>(srcObjSet);
        vo3.setName("vo_3_new");
        if ("vo_3_new".equals(destObjList.get(0).getName())
                || "vo_3_new".equals(destObjList.get(1).getName())) {
            System.out.println("Set -> List for Bean : 浅度copy");
        } else {
            System.out.println("Set -> List for Bean : 深度copy");
        }
        System.out.println("==============================");

执行结果：

引用

==============================
List -> Set
List -> Set 集合中元素的顺序不变
List -> Set for String : 深度copy
List -> Set for Bean : 浅度copy
Set -> List
List -> Set 集合中元素的顺序会变
Set -> List for String : 深度copy
Set -> List for Bean : 浅度copy
==============================

【四】、 List <-> Collection

  System.out.println("==============================");
        System.out.println("List -> Collection");
        List<String> list = new ArrayList<String>();
        list.add("michael");
        list.add("xiaoxiao");
        Collection<String> destCol = list;
        System.out.println("destCol size:" + destCol.size());
        System.out.println("List继承于Collection，可以直接赋值");

        System.out.println("Collection -> List");
        Collection<String> col = new ArrayList<String>();
        col.add("michael");
        col.add("xiaoxiao");
        List<String> destList = new ArrayList<String>(col);
        System.out.println("destList size:" + destList.size());

        System.out.println("==============================");

执行结果：

引用

==============================
List -> Collection
destCol size:2
List继承于Collection，可以直接赋值
Collection -> List
destList size:2
==============================

【五】、 Array Copy

System.out.println("==============================");
        System.out.println("Array Copy :String");
        String[] srcArr = new String[] { "michael", "xiaoxiao" };
        String[] destArr = new String[srcArr.length];

        System.arraycopy(srcArr, 0, destArr, 0, srcArr.length);

        System.out.println("Array Copy : Bean");

        TestVo vo1 = new TestVo("michael");
        TestVo[] srcObjArr = new TestVo[] { vo1, new TestVo("xiaoxiao") };
        TestVo[] destObjArr = new TestVo[srcArr.length];

        System.arraycopy(srcObjArr, 0, destObjArr, 0, srcObjArr.length);
        vo1.setName("michael_new");
        System.out.println("srcObjArr[0]的属性name修改为：michael_new");
        System.out
                .println("destObjArr[0]的属性name当前值：" + destObjArr[0].getName());
        if (srcObjArr[0] == destObjArr[0]) {
            System.out.println("Array Copy for Bean : 浅度copy");
        } else {
            System.out.println("Array Copy for Bean : 深度copy");
        }
        System.out.println("==============================");

执行结果：

引用

==============================
Array Copy :String
Array Copy : Bean
srcObjArr[0]的属性name修改为：michael_new
destObjArr[0]的属性name当前值：michael_new
Array Copy for Bean : 浅度copy
==============================

【六】、 List Copy

System.out.println("==============================");
        System.out.println("List Copy :String");

        List<String> srcList = new ArrayList<String>();
        srcList.add("michael");
        srcList.add("xiaoxiao");

        List<String> descList = srcList;

        List<String> descList2 = new ArrayList<String>(srcList);

        List<String> descList3 = new ArrayList<String>(Arrays
                .asList(new String[srcList.size()]));
        Collections.copy(descList3, srcList);

        srcList.clear();
        System.out.println("源List清空");
        System.out.println("直接赋值descList = srcList 的方法copy后的List     size: "
                + descList.size());
        System.out.println("new ArrayList<String>(srcList)的方法copy后的List size: "
                + descList2.size());
        System.out.println("Collections.copy(dest,src)的方法copy后的List     size: "
                + descList3.size());

        System.out.println("==============================");

执行结果：

引用

==============================
List Copy :String
源List清空
直接赋值descList = srcList 的方法copy后的List     size: 0
new ArrayList<String>(srcList)的方法copy后的List size: 2
Collections.copy(dest,src)的方法copy后的List     size: 2
==============================

转载请注明来自：Michael's blog @http://sjsky.iteye.com/

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