int apples = 5; 
int pears = apples; 

class Student { 
  private int number; 
 
  public int getNumber() { 
    return number; 
  } 
 
  public void setNumber(int number) { 
    this.number = number; 
  } 
   
} 
public class Test { 
   
  public static void main(String args[]) { 
    Student stu1 = new Student(); 
    stu1.setNumber(12345); 
    Student stu2 = stu1; 
     
    System.out.println("学生1:" + stu1.getNumber()); 
    System.out.println("学生2:" + stu2.getNumber()); 
  } 
}

stu2.setNumber(54321); 
 
System.out.println("学生1:" + stu1.getNumber()); 
System.out.println("学生2:" + stu2.getNumber()); 

/*
Creates and returns a copy of this object. The precise meaning of "copy" may depend on the class of the object.
The general intent is that, for any object x, the expression:
1) x.clone() != x will be true
2) x.clone().getClass() == x.getClass() will be true, but these are not absolute requirements.
3) x.clone().equals(x) will be true, this is not an absolute requirement.
*/
protected native Object clone() throws CloneNotSupportedException;

class Student implements Cloneable{
 private int number;
 public int getNumber() {
  return number;
 }
 public void setNumber(int number) {
  this.number = number;
 }
 @Override 
   public Object clone() {
  Student stu = null;
  try{
   stu = (Student)super.clone();
  }
  catch(CloneNotSupportedException e) {
   e.printStackTrace();
  }
  return stu;
 }
}
public class Test {
 public static void main(String args[]) {
  Student stu1 = new Student();
  stu1.setNumber(12345);
  Student stu2 = (Student)stu1.clone();
  System.out.println("学生1:" + stu1.getNumber());
  System.out.println("学生2:" + stu2.getNumber());
  stu2.setNumber(54321);
  System.out.println("学生1:" + stu1.getNumber());
  System.out.println("学生2:" + stu2.getNumber());
 }
}

System.out.println(stu1 == stu2); // false 

class Address {
 private String add;
 public String getAdd() {
  return add;
 }
 public void setAdd(String add) {
  this.add = add;
 }
}
class Student implements Cloneable{
 private int number;
 private Address addr;
 public Address getAddr() {
  return addr;
 }
 public void setAddr(Address addr) {
  this.addr = addr;
 }
 public int getNumber() {
  return number;
 }
 public void setNumber(int number) {
  this.number = number;
 }
 @Override 
   public Object clone() {
  Student stu = null;
  try{
   stu = (Student)super.clone();
  }
  catch(CloneNotSupportedException e) {
   e.printStackTrace();
  }
  return stu;
 }
}
public class Test {
 public static void main(String args[]) {
  Address addr = new Address();
  addr.setAdd("杭州市");
  Student stu1 = new Student();
  stu1.setNumber(123);
  stu1.setAddr(addr);
  Student stu2 = (Student)stu1.clone();
  System.out.println("学生1:" + stu1.getNumber() + ",地址:" + stu1.getAddr().getAdd());
  System.out.println("学生2:" + stu2.getNumber() + ",地址:" + stu2.getAddr().getAdd());
 }
}

addr.setAdd("西湖区"); 
 
System.out.println("学生1:" + stu1.getNumber() + ",地址:" + stu1.getAddr().getAdd()); 
System.out.println("学生2:" + stu2.getNumber() + ",地址:" + stu2.getAddr().getAdd()); 

学生1:123,地址:杭州市 
学生2:123,地址:杭州市 
学生1:123,地址:西湖区 
学生2:123,地址:西湖区 

package abc; 
 
class Address implements Cloneable { 
  private String add; 
 
  public String getAdd() { 
    return add; 
  } 
 
  public void setAdd(String add) { 
    this.add = add; 
  } 
   
  @Override 
  public Object clone() { 
    Address addr = null; 
    try{ 
      addr = (Address)super.clone(); 
    }catch(CloneNotSupportedException e) { 
      e.printStackTrace(); 
    } 
    return addr; 
  } 
} 
 
class Student implements Cloneable{ 
  private int number; 
 
  private Address addr; 
   
  public Address getAddr() { 
    return addr; 
  } 
 
  public void setAddr(Address addr) { 
    this.addr = addr; 
  } 
 
  public int getNumber() { 
    return number; 
  } 
 
  public void setNumber(int number) { 
    this.number = number; 
  } 
   
  @Override 
  public Object clone() { 
    Student stu = null; 
    try{ 
      stu = (Student)super.clone();  //浅复制 
    }catch(CloneNotSupportedException e) { 
      e.printStackTrace(); 
    } 
    stu.addr = (Address)addr.clone();  //深度复制 
    return stu; 
  } 
} 
public class Test { 
   
  public static void main(String args[]) { 
     
    Address addr = new Address(); 
    addr.setAdd("杭州市"); 
    Student stu1 = new Student(); 
    stu1.setNumber(123); 
    stu1.setAddr(addr); 
     
    Student stu2 = (Student)stu1.clone(); 
     
    System.out.println("学生1:" + stu1.getNumber() + ",地址:" + stu1.getAddr().getAdd()); 
    System.out.println("学生2:" + stu2.getNumber() + ",地址:" + stu2.getAddr().getAdd()); 
     
    addr.setAdd("西湖区"); 
     
    System.out.println("学生1:" + stu1.getNumber() + ",地址:" + stu1.getAddr().getAdd()); 
    System.out.println("学生2:" + stu2.getNumber() + ",地址:" + stu2.getAddr().getAdd()); 
  } 
}

/** 
 * Return a copy of this object. 
 */ 
public Object clone() { 
  Date d = null; 
  try { 
    d = (Date)super.clone(); 
    if (cdate != null) { 
      d.cdate = (BaseCalendar.Date) cdate.clone(); 
    } 
  } catch (CloneNotSupportedException e) {} // Won't happen 
  return d; 
}

public class Outer implements Serializable{
 private static final long serialVersionUID = 369285298572941L; //最好是显式声明ID
 public Inner inner;
　//Discription:[深度复制方法,需要对象及对象所有的对象属性都实现序列化]　
 public Outer myclone() {
   Outer outer = null;
   try { // 将该对象序列化成流,因为写在流里的是对象的一个拷贝，而原对象仍然存在于JVM里面。所以利用这个特性可以实现对象的深拷贝
     ByteArrayOutputStream baos = new ByteArrayOutputStream();
     ObjectOutputStream oos = new ObjectOutputStream(baos);
     oos.writeObject(this);
　　　　　　// 将流序列化成对象
     ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
     ObjectInputStream ois = new ObjectInputStream(bais);
     outer = (Outer) ois.readObject();
   } catch (IOException e) {
     e.printStackTrace();
   } catch (ClassNotFoundException e) {
     e.printStackTrace();
   }
   return outer;
 }
}

public class Inner implements Serializable{
 private static final long serialVersionUID = 872390113109L; //最好是显式声明ID
 public String name = "";

 public Inner(String name) {
   this.name = name;
 }

 @Override
 public String toString() {
   return "Inner的name值为：" + name;
 }
}