ArrayList clone（）– ArrayList深拷贝和浅拷贝

示例程序以ArrayList克隆方法为例。学生对象上的ArrayList深层复制和浅层复制示例。

1.简介

ArrayList clone（）– ArrayList深复制和浅复制 。 ArrayList clone（）方法用于创建list的浅表副本 。在新列表中，仅复制对象引用。如果我们在第一个ArrayList中更改对象状态，则更改后的对象状态也将反映在克隆的ArrayList中。

2. ArrayList克隆–浅拷贝示例

将字符串列表复制到花药列表的示例程序
clone（） 。

 package com.java.w3schools.blog.arraylist;  import java.util.ArrayList;  import java.util.List;  /** * * Java ArrayList Clone Example * * @author Java8Example blog * */  public class ArrayListCloneExample { public static void main(String[] args) { ArrayList<String> list = new ArrayList<>(); list.add( "one" ); list.add( "two" ); list.add( "three" ); list.add( "four" ); list.add( "give" ); System.out.println( "Before clone : " + list); ArrayList clonedLis = (ArrayList) list.clone();   System.out.println( "After clone : " +clonedLis); }  }

输出：

 Before clone : [one, two, three, four, give]  After clone : [one, two, three, four, give]

3. ArrayList克隆–自定义浅复制示例

示例程序将ArrayList与自定义对象进行浅表复制。对克隆对象的修改反映在原始对象中。观察该程序的输出。

 package com.java.w3schools.blog.arraylist;  import java.util.ArrayList;  /** * * Java ArrayList Clone Example with custom object * * @author Java8Example blog * */  public class ArrayListShalloCloneExample { public static void main(String[] args) { ArrayList<Student> list = new ArrayList<>(); list.add( new Student( 100 , "harish" )); list.add( new Student( 101 , "Jayaram" )); ArrayList<Student> clonedList = (ArrayList) list.clone(); Student student = clonedList.get( 1 ); student.setName( "Jhon" ); System.out.println( "Cloned list : " + clonedList); System.out.println( "Original list : " + list); }  }  class Student { private int id; private String name; public Student( int id, String name) { super (); this .id = id; this .name = name; } public int getId() { return id; } public void setId( int id) { this .id = id; } public String getName() { return name; } public void setName(String name) { this .name = name; } @Override public String toString() { return "Student [id=" + id + ", name=" + name + "]" ; }  }

输出：

 Cloned list : [Student [id= 100 , name=harish], Student [id= 101 , name=Jhon]]  Original list : [Student [id= 100 , name=harish], Student [id= 101 , name=Jhon]]

4. ArrayList克隆–深度复制示例

下面的程序创建对象的深层副本。对克隆列表的修改不会影响原始列表。

 public class ArrayListDeepCloneExample { public static void main(String[] args) { ArrayList<Student> list = new ArrayList<>(); list.add( new Student( 100 , "harish" )); list.add( new Student( 101 , "Jayaram" )); ArrayList<Student> clonedList = new ArrayList<>(); Iterator<Student> it = list.iterator(); while (it.hasNext()) { Student s = it.next(); Student newS = new Student(s.getId(), s.getName()); clonedList.add(newS); } Student student = clonedList.get( 1 ); student.setName( "Jhon" ); System.out.println( "Cloned list : " + clonedList); System.out.println( "Original list : " + list); }  }

输出：

 Cloned list : [Student [id= 100 , name=harish], Student [id= 101 , name=Jhon]]  Original list : [Student [id= 100 , name=harish], Student [id= 101 , name=Jayaram]]