shallow copy 和 deep copy 的示例

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本文属原创，转载请注明出处：http://www.cnblogs.com/robinjava77/p/5481874.html (Robin)

Student

 1 package base; 2  3 import java.io.Serializable; 4  5 /** 6  * Created by robin on 2016/5/11. 7  * 8  * @author robin 9  */10 public class Student implements Cloneable,Serializable{11 12     private String stuId;13 14     private String name;15 16     private Integer age;17 18     public Student(String stuId, String name, Integer age) {19         this.stuId = stuId;20         this.name = name;21         this.age = age;22     }23 24     public Student(String stuId, String name) {25         this.stuId = stuId;26         this.name = name;27     }28 29     public String getStuId() {30         return stuId;31     }32 33     public String getName() {34         return name;35     }36 37     public Integer getAge() {38         return age;39     }40 41     public void setStuId(String stuId) {42         this.stuId = stuId;43     }44 45     public void setName(String name) {46         this.name = name;47     }48 49     public void setAge(Integer age) {50         this.age = age;51     }52     /**53      * @return 创建并返回此对象的一个副本。54      * @throws CloneNotSupportedException55      */56     public Student clone() throws CloneNotSupportedException {57         //直接调用父类的clone()方法,返回克隆副本58         return (Student) super.clone();59     }60 61     @Override62     public String toString(){63         StringBuffer sb = new StringBuffer();64         sb.append("[stuId:");65         sb.append(this.stuId);66         sb.append(",name:");67         sb.append(this.name);68         sb.append(",age:");69         sb.append(this.age);70         sb.append("]");71         return sb.toString();72     }73 74     /**75      * JAVA当中所有的类都是继承于Object这个基类的，在Object中的基类中定义了一个equals的方法，这个方法的初始行为是比较对象的内存地址。76      * 但在一些类库当中这个方法被覆盖掉了，如String,Integer,Date在这些类当中equals有其自身的实现，而不再是比较类在堆内存中的存放地址了。77      * 注意：对于复合数据类型之间进行equals比较，在没有覆写equals方法的情况下，他们之间的比较还是基于他们在内存中的存放位置的地址值。78      * @param student79      * @return80      */81     public boolean equals(Student student){82         if(this.stuId.equals(student.getStuId()) &&83                 this.age.equals(student.getAge()) &&84                 this.name.equals(student.getName())){85             return true;86         }87         return false;88     }89 }

深度拷贝和浅层拷贝的区别代码示例

  1 package base;  2   3 import java.io.*;  4 import java.util.ArrayList;  5 import java.util.List;  6 import java.util.Vector;  7   8 /**  9  * Created by robin on 2016/5/11. 10  * 11  * @author robin 12  */ 13 public class ShallowAndDeepCopy { 14  15     private static List<Student> noumenon = new Vector<Student>(); 16  17     private static void initPublicNums(){ 18         for (int i =0;i < 5;i++){ 19             Student newStu = new Student(""+i,"name:"+i,i); 20             noumenon.add(newStu); 21         } 22     } 23  24     public static void main(String args[]) throws CloneNotSupportedException { 25         initPublicNums(); 26         List<Student> quote = noumenon; 27         List<Student> shallowCopy = getPublicNumsShallow(); 28         List<Student> deepCopy = getPublicNumsDeep(); 29         List<Student> deepCommonCopy = deepCopy(noumenon); 30         System.out.println("quote List的内存地址是否相同："+(noumenon == quote)); 31         System.out.println("shallow copy List的内存地址是否相同："+(noumenon == shallowCopy)); 32         System.out.println("deep copy List的内存地址是否相同：" + (noumenon == deepCopy)); 33         System.out.println("deepCommon copy List的内存地址是否相同：" + (noumenon == deepCommonCopy)); 34         System.out.println("------------------shallow copy test-----------------------"); 35         for (int i=0;i<shallowCopy.size();i++){ 36             Student shallowStu = shallowCopy.get(i); 37             Student noumenonStu = noumenon.get(i); 38             System.out.println("{shallowStu  detail:" + shallowStu.toString()+"}"); 39             System.out.println("{noumenonStu detail:" + noumenonStu.toString()+"}"); 40             System.out.println("{shallowStu equals noumenonStu:" + shallowStu.equals(noumenonStu)+"}"); 41             System.out.println("{shallowCopy("+i+")与noumenon("+i+")内存地址相同："+(noumenonStu == shallowStu)+"}"); 42             System.out.println(); 43         } 44         System.out.println("------------------deep copy test-----------------------"); 45         for (int i=0;i<deepCopy.size();i++){ 46             Student deepStu = deepCopy.get(i); 47             Student noumenonStu = ShallowAndDeepCopy.noumenon.get(i); 48             System.out.println("{deepStu     detail:" + deepStu.toString() + "}"); 49             System.out.println("{noumenonStu detail:" + noumenonStu.toString() + "}"); 50             System.out.println("{deepStu equals noumenonStu:" + deepStu.equals(noumenonStu) + "}"); 51             System.out.println("{deepCopy("+i+")与noumenon("+i+")内存地址相同："+(noumenonStu == deepStu)+"}"); 52             System.out.println(); 53         } 54         System.out.println("------------------deepCommonCopy copy test-----------------------"); 55         for (int i=0;i<deepCommonCopy.size();i++){ 56             Student deepCommonStu = deepCommonCopy.get(i); 57             Student noumenonStu = ShallowAndDeepCopy.noumenon.get(i); 58             System.out.println("{deepCommonStu detail:" + deepCommonStu.toString() + "}"); 59             System.out.println("{noumenonStu   detail:" + noumenonStu.toString() + "}"); 60             System.out.println("{deepCommonStu equals noumenonStu:" + deepCommonStu.equals(noumenonStu) + "}"); 61             System.out.println("{deepCommonCopy("+i+")与noumenon("+i+")内存地址相同："+(noumenonStu == deepCommonStu)+"}"); 62             System.out.println(); 63         } 64     } 65  66     /** 67      * shallow copy:list中 元素引用 仍然是相同的 68      * @return 69      */ 70     private static List<Student> getPublicNumsShallow(){ 71         List<Student> clone = new ArrayList<Student>(noumenon); 72         return clone; 73     } 74  75     /** 76      * deep copy:list中 引用元素 地址是不同的 77      * @return 78      * @throws CloneNotSupportedException 79      */ 80     private static List<Student> getPublicNumsDeep() throws CloneNotSupportedException { 81         List<Student> clone = new ArrayList<Student>(); 82         for (int i=0;i< noumenon.size();i++){ 83             clone.add(noumenon.get(i).clone()); 84         } 85         return clone; 86     } 87  88     /** 89      * 深度复制 这种实现的深度复制，是不需要被复制的元素实现clone方法的 但JDK版本要求：1.7及以上 90      * @param src  这个是同事完成 非本人开发 91      * @return 92      */ 93     private static List deepCopy(List src) { 94         List dest = null; 95         ByteArrayInputStream byteIn = null; 96         ObjectInputStream in = null; 97         try (ByteArrayOutputStream byteOut = new ByteArrayOutputStream(); 98              ObjectOutputStream out = new ObjectOutputStream(byteOut)) { 99             out.writeObject(src);100             byteIn = new ByteArrayInputStream(byteOut.toByteArray());101             in = new ObjectInputStream(byteIn);102             dest = (List) in.readObject();103         } catch (IOException | ClassNotFoundException e) {104             e.printStackTrace();105         } finally {106             try {107                 if (in != null) {108                     in.close();109                 }110                 if (byteIn != null) {111                     byteIn.close();112                 }113             } catch (IOException e) {114                 e.printStackTrace();115             }116         }117         return dest;118     }119 120 121 }

执行结果：

 1 quote List的内存地址是否相同：true 2 shallow copy List的内存地址是否相同：false 3 deep copy List的内存地址是否相同：false 4 deepCommon copy List的内存地址是否相同：false 5 ------------------shallow copy test----------------------- 6 {shallowStu  detail:[stuId:0,name:name:0,age:0]} 7 {noumenonStu detail:[stuId:0,name:name:0,age:0]} 8 {shallowStu equals noumenonStu:true} 9 {shallowCopy(0)与noumenon(0)内存地址相同：true}10 11 {shallowStu  detail:[stuId:1,name:name:1,age:1]}12 {noumenonStu detail:[stuId:1,name:name:1,age:1]}13 {shallowStu equals noumenonStu:true}14 {shallowCopy(1)与noumenon(1)内存地址相同：true}15 16 {shallowStu  detail:[stuId:2,name:name:2,age:2]}17 {noumenonStu detail:[stuId:2,name:name:2,age:2]}18 {shallowStu equals noumenonStu:true}19 {shallowCopy(2)与noumenon(2)内存地址相同：true}20 21 {shallowStu  detail:[stuId:3,name:name:3,age:3]}22 {noumenonStu detail:[stuId:3,name:name:3,age:3]}23 {shallowStu equals noumenonStu:true}24 {shallowCopy(3)与noumenon(3)内存地址相同：true}25 26 {shallowStu  detail:[stuId:4,name:name:4,age:4]}27 {noumenonStu detail:[stuId:4,name:name:4,age:4]}28 {shallowStu equals noumenonStu:true}29 {shallowCopy(4)与noumenon(4)内存地址相同：true}30 31 ------------------deep copy test-----------------------32 {deepStu     detail:[stuId:0,name:name:0,age:0]}33 {noumenonStu detail:[stuId:0,name:name:0,age:0]}34 {deepStu equals noumenonStu:true}35 {deepCopy(0)与noumenon(0)内存地址相同：false}36 37 {deepStu     detail:[stuId:1,name:name:1,age:1]}38 {noumenonStu detail:[stuId:1,name:name:1,age:1]}39 {deepStu equals noumenonStu:true}40 {deepCopy(1)与noumenon(1)内存地址相同：false}41 42 {deepStu     detail:[stuId:2,name:name:2,age:2]}43 {noumenonStu detail:[stuId:2,name:name:2,age:2]}44 {deepStu equals noumenonStu:true}45 {deepCopy(2)与noumenon(2)内存地址相同：false}46 47 {deepStu     detail:[stuId:3,name:name:3,age:3]}48 {noumenonStu detail:[stuId:3,name:name:3,age:3]}49 {deepStu equals noumenonStu:true}50 {deepCopy(3)与noumenon(3)内存地址相同：false}51 52 {deepStu     detail:[stuId:4,name:name:4,age:4]}53 {noumenonStu detail:[stuId:4,name:name:4,age:4]}54 {deepStu equals noumenonStu:true}55 {deepCopy(4)与noumenon(4)内存地址相同：false}56 57 ------------------deepCommonCopy copy test-----------------------58 {deepCommonStu detail:[stuId:0,name:name:0,age:0]}59 {noumenonStu   detail:[stuId:0,name:name:0,age:0]}60 {deepCommonStu equals noumenonStu:true}61 {deepCommonCopy(0)与noumenon(0)内存地址相同：false}62 63 {deepCommonStu detail:[stuId:1,name:name:1,age:1]}64 {noumenonStu   detail:[stuId:1,name:name:1,age:1]}65 {deepCommonStu equals noumenonStu:true}66 {deepCommonCopy(1)与noumenon(1)内存地址相同：false}67 68 {deepCommonStu detail:[stuId:2,name:name:2,age:2]}69 {noumenonStu   detail:[stuId:2,name:name:2,age:2]}70 {deepCommonStu equals noumenonStu:true}71 {deepCommonCopy(2)与noumenon(2)内存地址相同：false}72 73 {deepCommonStu detail:[stuId:3,name:name:3,age:3]}74 {noumenonStu   detail:[stuId:3,name:name:3,age:3]}75 {deepCommonStu equals noumenonStu:true}76 {deepCommonCopy(3)与noumenon(3)内存地址相同：false}77 78 {deepCommonStu detail:[stuId:4,name:name:4,age:4]}79 {noumenonStu   detail:[stuId:4,name:name:4,age:4]}80 {deepCommonStu equals noumenonStu:true}81 {deepCommonCopy(4)与noumenon(4)内存地址相同：false}

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