Java，
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Java，
(1)废话：最近有点心不在焉，看这个知道一点，看那个也知道一点。在看看，这个也不会，那个也不会，纠结而又操蛋的人生。
(2)走着：需要一个JavaBean：TestVo.java只有一个字段name，这里就不把代码贴出来。
1、List->Array
1 System.out.println("===============List转化为Array==============="); 2 List<String> list1 = new ArrayList<String>(); 3 list1.add("list_a"); 4 list1.add("list_b"); 5 String[] array1 = list1.toArray(new String[list1.size()]); 6 System.out.println("array1="+Arrays.toString(array1)); 7 list1.clear(); 8 System.out.println("list1 clear()"); 9 System.out.println("list1.size=" + list1.size()+";array1.lenth="+array1.length); 10 if (array1.length == 2) { 11 System.out.println("List--->Array for String : 深度copy"); 12 } else { 13 System.out.println("List--->Array for String : 浅度copy"); 14 } 15 System.out.println("===============(bean)List转化为Array========"); 16 List<TestVo> voList1 = new ArrayList<TestVo>(); 17 TestVo vo1 = new TestVo("vo_a"); 18 voList1.add(vo1); 19 voList1.add(new TestVo("vo_b")); 20 TestVo[] voArray1 = voList1.toArray(new TestVo[voList1.size()]); 21 System.out.println("voArray1.length="+voArray1.length); 22 vo1.setName("vo_a_new"); 23 System.out.println("voList1[0]的属性Name修改为：vo_a_new;"+"voArray1[0]的属性Name当前值：" + voArray1[0].getName()); 24 if ("vo_a_new".equals(voArray1[0].getName())) { 25 System.out.println("List ---> Array for Bean : 浅度copy"); 26 } else { 27 System.out.println("List ---> Array for Bean : 深度copy"); 28 } 29 30 System.out.println("===============Array转化为List==============="); 31 String[] array2 = new String[] { "arr_a", "arr_b" }; 32 List<String> list2 = Arrays.asList(array2); 33 array2[0] = "arr_a_new"; 34 if ("arr_a_new".equals(list2.get(0))) { 35 System.out.println("Array ---> List for String : 深度copy"); 36 } else { 37 System.out.println("Array ---> List for String : 浅度copy"); 38 } 39 40 System.out.println("===============(bean)Array转化为List========"); 41 TestVo vo3 = new TestVo("vo_a"); 42 TestVo[] voArray2 = new TestVo[] {vo3, new TestVo("vo_b") }; 43 List<TestVo> voList2 = Arrays.asList(voArray2); 44 vo3.setName("vo_a_new"); 45 System.out.println("voArray2[0]的属性Name修改为：vo_a_new;"+"voList2[0]的属性Name当前值："+ voList2.get(0).getName()); 46 if ("vo_a_new".equals(voList2.get(0).getName())) { 47 System.out.println("Array -> List for Bean : 浅度copy"); 48 } else { 49 System.out.println("Array -> List for Bean : 深度copy"); 50 }
执行结果:
===============List转化为Array=============== array1=[list_a, list_b] list1 clear() list1.size=0;array1.lenth=2 List--->Array for String : 深度copy ===============(bean)List转化为Array======== voArray1.length=2 voList1[0]的属性Name修改为：vo_a_new;voArray1[0]的属性Name当前值：vo_a_new List ---> Array for Bean : 浅度copy ===============Array转化为List=============== Array ---> List for String : 深度copy ===============(bean)Array转化为List======== voArray2[0]的属性Name修改为：vo_a_new;voList2[0]的属性Name当前值：vo_a_new Array -> List for Bean : 浅度copy
2、Set->Array
1 System.out.println("===============Set转化为Array==============="); 2 Set<String> set1 = new HashSet<String>(); 3 set1.add("set_a"); 4 set1.add("set_b"); 5 String[] array1 = set1.toArray(new String[set1.size()]); 6 System.out.println("set1="+set1.toString()); 7 System.out.println("array1="+Arrays.toString(array1)); 8 set1.clear(); 9 if (array1.length==2) { 10 System.out.println("Set ---> Array for String: 深度copy"); 11 } else { 12 System.out.println("Set ----> Array for String: 浅度copy"); 13 } 14 System.out.println("==========(bean)Set转化为Array=========="); 15 Set<TestVo> voSet1 = new HashSet<TestVo>(); 16 TestVo vo1 = new TestVo("vo_a"); 17 voSet1.add(vo1); 18 voSet1.add(new TestVo("vo_b")); 19 TestVo[] voArray1 = voSet1.toArray(new TestVo[voSet1.size()]); 20 vo1.setName("vo_a_new"); 21 System.out.println("voArray1.length="+voArray1.length); 22 boolean deepFlag = true; 23 for (TestVo vo : voArray1) { 24 if ("vo_a_new".equals(vo.getName())) { 25 deepFlag = false; 26 break; 27 } 28 } 29 if (deepFlag) { 30 System.out.println("Set ---> Array for Bean : 深度copy"); 31 } else { 32 System.out.println("Set ---> Array for Bean : 浅度copy"); 33 } 34 35 System.out.println("===============Array转化为Set==============="); 36 String[] array2 = new String[] { "arr_a", "arr_b" }; 37 Set<String> set2 = new HashSet<String>(Arrays.asList(array2)); 38 array2[0]="arr_a_new"; 39 System.out.println("Array ---> Set for String set2= " + set2.toString()); 40 if(set2.contains("arr_a_new")){ 41 System.out.println("Array ---> Set for String: 浅度copy"); 42 }else{ 43 System.out.println("Array ---> Set for String: 深度copy"); 44 } 45 System.out.println("============(bean)Array转化为Set============"); 46 TestVo vo3 = new TestVo("vo_a"); 47 TestVo[] voArray2 = new TestVo[] { vo1, new TestVo("vo_b") }; 48 Set<TestVo> voSet2 = new HashSet<TestVo>(Arrays.asList(voArray2)); 49 vo3.setName("vo_a_new"); 50 for(java.util.Iterator it=voSet2.iterator();it.hasNext();){ 51 TestVo vo=(TestVo) it.next(); 52 if (vo.getName().equals("vo_a_new")) { 53 System.out.println("Array ---> Set for Bean : 浅度copy"); 54 } else { 55 System.out.println("Array ---> Set for Bean : 深度copy"); 56 } 57 }
执行结果：
===============Set转化为Array=============== set1=[set_a, set_b] array1=[set_a, set_b] Set ---> Array for String: 深度copy ==========(bean)Set转化为Array========== voArray1.length=2 Set ---> Array for Bean : 浅度copy ===============Array转化为Set=============== Array ---> Set for String set2= [arr_a, arr_b] Array ---> Set for String: 深度copy ============(bean)Array转化为Set============ Array ---> Set for Bean : 浅度copy Array ---> Set for Bean : 深度copy
3、List->Set
1 System.out.println("===============List转化为Set==============="); 2 List<String> list1 = new ArrayList<String>(); 3 list1.add("list_a"); 4 list1.add("list_b"); 5 Set<String> set1 = new HashSet<String>(list1); 6 System.out.println("list1="+list1.toString()); 7 System.out.println("set1="+set1.toString()); 8 list1.clear(); 9 System.out.println("list1.clear()"); 10 if (set1.size() == 2) { 11 System.out.println("List ---> Set for String : 深度copy"); 12 } else { 13 System.out.println("List ---> Set for String : 浅度copy"); 14 } 15 System.out.println("===============(bean)List转化为Set==========="); 16 List<TestVo> voList1 = new ArrayList<TestVo>(); 17 TestVo vo1 = new TestVo("vo_a"); 18 voList1.add(vo1); 19 voList1.add(new TestVo("vo_b")); 20 Set<TestVo> voSet1 = new HashSet<TestVo>(voList1); 21 vo1.setName("vo_a_new"); 22 boolean setflag=false; 23 for(java.util.Iterator it=voSet1.iterator();it.hasNext();){ 24 TestVo vo=(TestVo) it.next(); 25 if (vo.getName().equals("vo_a_new")) { 26 setflag=true; 27 } 28 } 29 if(setflag){ 30 System.out.println("Array ---> Set for Bean : 浅度copy"); 31 } else { 32 System.out.println("Array ---> Set for Bean : 深度copy"); 33 } 34 System.out.println("===============Set转化为List==============="); 35 Set<String> set2 = new HashSet<String>(); 36 set2.add("set_a"); 37 set2.add("set_b"); 38 List<String> list2 = new ArrayList<String>(set2); 39 set2.clear(); 40 if (list2.size() == 2) { 41 System.out.println("Set ---> List for String : 深度copy"); 42 } else { 43 System.out.println("Set ---> List for String : 浅度copy"); 44 } 45 System.out.println("===============(bean)Set转化为List==========="); 46 Set<TestVo> voSet2 = new HashSet<TestVo>(); 47 TestVo vo3 = new TestVo("vo_a"); 48 voSet2.add(vo3); 49 voSet2.add(new TestVo("vo_b")); 50 List<TestVo> voList2 = new ArrayList<TestVo>(voSet2); 51 vo3.setName("vo_a_new"); 52 boolean listflag=false; 53 for(TestVo vo:voList2){ 54 if(vo.getName().equals("vo_a_new")){ 55 listflag=true; 56 } 57 } 58 if (listflag) { 59 System.out.println("Set ---> List for Bean : 浅度copy"); 60 } else { 61 System.out.println("Set ---> List for Bean : 深度copy"); 62 }
执行结果：
===============List转化为Set=============== list1=[list_a, list_b] set1=[list_b, list_a] list1.clear() List ---> Set for String : 深度copy ===============(bean)List转化为Set=========== Array ---> Set for Bean : 浅度copy ===============Set转化为List=============== Set ---> List for String : 深度copy ===============(bean)Set转化为List=========== Set ---> List for Bean : 浅度copy
4、List->Collection
1 System.out.println("===============List转化为Colletction==============="); 2 List<String> list1 = new ArrayList<String>(); 3 list1.add("list_a"); 4 list1.add("list_b"); 5 Collection<String> collection1 = list1; 6 System.out.println("collection1.size:" + collection1.size()); 7 System.out.println("List继承于Collection，可以直接赋值"); 8 9 System.out.println("===============Collection转化为List==============="); 10 Collection<String> collection2 = new ArrayList<String>(); 11 collection2.add("col_a"); 12 collection2.add("col_b"); 13 List<String> list2 = new ArrayList<String>(collection2); 14 System.out.println("list2="+list2.toString());
执行结果：
===============List转化为Colletction=============== collection1.size:2 List继承于Collection，可以直接赋值 ===============Collection转化为List=============== list2=[col_a, col_b]
5、ArrayCopy
1 System.out.println("===============Arraycopy==============="); 2 String[] array1 = new String[] { "arr_a", "arr_b" }; 3 String[] array2 = new String[array1.length]; 4 System.arraycopy(array1, 0, array2, 0, array1.length); 5 array1[0]="arr_a_new"; 6 System.out.println("array2="+Arrays.toString(array2)); 7 if(array2[0]=="arr_a_new"){ 8 System.out.println("Array Copy for String :浅度copy"); 9 }else{ 10 System.out.println("Array Copy for String :深度copy"); 11 } 12 System.out.println("===============(bean)Arraycopy==============="); 13 TestVo vo1 = new TestVo("vo_a"); 14 TestVo[] voArray1 = new TestVo[] { vo1, new TestVo("vo_b") }; 15 TestVo[] voArray2 = new TestVo[voArray1.length]; 16 System.arraycopy(voArray1, 0, voArray2, 0, voArray1.length); 17 vo1.setName("vo_a_new"); 18 System.out.println("voArray1[0]的属性name修改为：vo_a_new;"+"voArray2[0]的属性name当前值：" + voArray2[0].getName()); 19 if (voArray1[0] == voArray2[0]) { 20 System.out.println("Array Copy for Bean : 浅度copy"); 21 } else { 22 System.out.println("Array Copy for Bean : 深度copy"); 23 }
执行结果：
===============Arraycopy=============== array2=[arr_a, arr_b] Array Copy for String :深度copy ===============(bean)Arraycopy=============== voArray1[0]的属性name修改为：vo_a_new;voArray2[0]的属性name当前值：vo_a_new Array Copy for Bean : 浅度copy
6、ListCopy
1 System.out.println("===============List copy==============="); 2 List<String> list1 = new ArrayList<String>(); 3 list1.add("list_a"); 4 list1.add("list_b"); 5 6 List<String> list2 = list1; 7 List<String> list3 = new ArrayList<String>(list1); 8 List<String> list4 = new ArrayList<String>(Arrays.asList(new String[list1.size()])); 9 Collections.copy(list4, list1); 10 list1.clear(); 11 System.out.println("List copy 源List清空"); 12 System.out.println("List copy 直接赋值list2 = list1 的方法copy后的List的size="+ list2.size()); 13 System.out.println("List copy new ArrayList<String>(list1)的方法copy后的List的size="+ list3.size()); 14 System.out.println("List copy Collections.copy(list4,list1)的方法copy后的List的size: "+ list4.size());
执行结果：
===============List copy=============== List copy 源List清空 List copy 直接赋值list2 = list1 的方法copy后的List的size=0 List copy new ArrayList<String>(list1)的方法copy后的List的size=2 List copy Collections.copy(list4,list1)的方法copy后的List的size: 2
(3)结束：这个文章是我借鉴一个同事写的博客，写下来一个是为了加深记忆，二是以防以后找不到，三是也许能对别人有些帮助。
摘抄地址：http://www.micmiu.com/lang/java/array-collection-copy/
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