java/se: add object#clone sample

Author: Alice52

java/javase/javase-common/src/main/java/cn/edu/ntu/java/javase/common/model/Employee.java

@@ -12,6 +12,16 @@ public class Employee implements Serializable {
     private double salary;
     private Address address;
 
+    /*
+        @Override
+        protected Object clone() throws CloneNotSupportedException {
+            Employee clone = (Employee) super.clone();
+            clone.address = (Address) clone.address.clone();
+
+            return clone;
+        }
+    */
+
     public Employee(String name, int age, double salary, Address address) {
         this.name = name;
         this.age = age;

java/javase/javase-syntax/src/main/java/cn/edu/ntu/java/javase/syntax/object/CloneTest.java

@@ -23,22 +23,6 @@ public class CloneTest {
     // *******************************************
     // 浅克隆
     // *******************************************
-
-    public static <T> T deepClone(T object) {
-        try {
-            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
-            ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
-            objectOutputStream.writeObject(object);
-            ByteArrayInputStream bais =
-                    new ByteArrayInputStream(byteArrayOutputStream.toByteArray());
-            ObjectInputStream objectInputStream = new ObjectInputStream(bais);
-            return (T) objectInputStream.readObject();
-        } catch (Exception e) {
-            e.printStackTrace();
-            return null;
-        }
-    }
-
     @Test
     public void testShadowClone4Map() {
         HashMap<String, Address> map = new HashMap<>();
@@ -49,10 +33,6 @@ public void testShadowClone4Map() {
         Assert.isTrue(clone.get("nanjing") == map.get("nanjing"));
     }
 
-    // *******************************************
-    // 深克隆
-    // *******************************************
-
     @Test
     public void testShadowClone4List() {
         ArrayList<Address> list = new ArrayList<>();
@@ -63,6 +43,23 @@ public void testShadowClone4List() {
         Assert.isTrue(clone.get(0) == list.get(0));
     }
 
+    // *******************************************
+    // 深克隆1: 序列化(小推荐)
+    // *******************************************
+    public static <T> T deepClone(T object) {
+        try {
+            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+            ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
+            objectOutputStream.writeObject(object);
+            ByteArrayInputStream bais =
+                    new ByteArrayInputStream(byteArrayOutputStream.toByteArray());
+            ObjectInputStream objectInputStream = new ObjectInputStream(bais);
+            return (T) objectInputStream.readObject();
+        } catch (Exception e) {
+            e.printStackTrace();
+            return null;
+        }
+    }
     /** 需要 Address & Employee 实现序列化接口 */
     @Test
     public void whenModifyingOriginalObject_thenSerializableShouldNotChange() {
@@ -76,6 +73,9 @@ public void whenModifyingOriginalObject_thenSerializableShouldNotChange() {
         Assert.isFalse(deepCopy.getAddress().getCity().equals(pm.getAddress().getCity()));
     }
 
+    // *******************************************
+    // 深克隆2: json(obj-str-obj)(小推荐)
+    // *******************************************
     /** 不需要 Address & Employee 实现序列化接口 */
     @Test
     public void whenModifyingOriginalObject_thenGsonCloneShouldNotChange() {
@@ -89,11 +89,7 @@ public void whenModifyingOriginalObject_thenGsonCloneShouldNotChange() {
         Assert.isFalse(deepCopy.getAddress().getCity().equals(pm.getAddress().getCity()));
     }
 
-    /**
-     * 不需要 Address & Employee 实现序列化接口
-     *
-     * @throws IOException
-     */
+    /** 不需要 Address & Employee 实现序列化接口 */
     @Test
     public void whenModifyingOriginalObject_thenJacksonCopyShouldNotChange() throws IOException {
         Address address = new Address("xuzhou", "jiangsu");
@@ -104,4 +100,14 @@ public void whenModifyingOriginalObject_thenJacksonCopyShouldNotChange() throws
         address.setCity("shanghai");
         Assert.isFalse(deepCopy.getAddress().getCity().equals(pm.getAddress().getCity()));
     }
+
+    // *******************************************
+    // 深克隆3: 递归 clone(小推荐), 逻辑上判断后复制
+    // *******************************************
+
+    // *******************************************
+    // 深克隆4: 重写最外层对象的 clone(不推荐)
+    // @see Employee#clone()
+    // *******************************************
+
 }