Map深度复制

目录

Map深度复制

1，new HashMap<>(Object);

2，Put All;

3，串行化复制;

总结：

如何对Map类型的数据进行深度复制，有几种方式呢？

1，new HashMap<>(Object);

代码：

public static void main(String[] args) throws IOException, ClassNotFoundException {

testNewMap();

}

public static void testNewMap(){

System.out.println("====== new HashMap<>(e) =======");

Map one = new HashMap<>();

one.put("one","fish");

Map two = new HashMap<>(one);

System.out.println("init: one: "+ one.toString());

System.out.println("init: two: "+ two.toString());

System.out.println("====== change to grass =======");

two.put("one","grass");

System.out.println("change: one: "+ one.toString());

System.out.println("change: two: "+ two.toString());

System.out.println();

}

使用 new HashMap<>(one) 的方式

结果：

====== new HashMap<>(e) =======

init: one: {one=fish}

init: two: {one=fish}

====== change to grass =======

change: one: {one=fish}

change: two: {one=grass}

2，Put All;

代码：

public static void main(String[] args) throws IOException, ClassNotFoundException {

testPutAllMap();

}

public static void testPutAllMap(){

System.out.println("====== put all map =======");

Map one = new HashMap<>();

one.put("one","fish");

Map two = new HashMap<>();

two.putAll(one);

System.out.println("init: one: "+ one.toString());

System.out.println("init: two: "+ two.toString());

System.out.println("====== change to monkey =======");

two.put("one","monkey");

System.out.println("change: one: "+ one.toString());

System.out.println("change: two: "+ two.toString());

System.out.println();

}

结果：

====== put all map =======

init: one: {one=fish}

init: two: {one=fish}

====== change to monkey =======

change: one: {one=fish}

change: two: {one=monkey}

这边会标黄，处理后会变成第一种的情况。

3，串行化复制;

代码：

public static void main(String[] args) throws IOException, ClassNotFoundException {

testDeepCopyMap();

}

public static void testDeepCopyMap() throws IOException, ClassNotFoundException {

System.out.println("====== DeepCopy Map =======");

Map one = new HashMap<>();

one.put("one","fish");

Map two = CloneUtils.cloneMap(one);;

System.out.println("init: one: "+ one.toString());

System.out.println("init: two: "+ two.toString());

System.out.println("====== change to snake =======");

two.put("one","snake");

System.out.println("change: one: "+ one.toString());

System.out.println("change: two: "+ two.toString());

System.out.println();

}

串行化代码：

public class CloneUtils {

public static T clone(T src) throws IOException, ClassNotFoundException {

ObjectInputStream ois = getInputStream(src);

//返回生成的新对象

@SuppressWarnings("unchecked")

T cloneObj = (T) ois.readObject();

ois.close();

return cloneObj;

}

public static List deepCopy(List src) throws IOException, ClassNotFoundException {

ObjectInputStream ois = getInputStream(src);

@SuppressWarnings("unchecked")

List dest = (List) ois.readObject();

ois.close();

return dest;

}

public static Map cloneMap(Map src) throws IOException, ClassNotFoundException {

ObjectInputStream ois = getInputStream(src);

@SuppressWarnings("unchecked")

Map result = (Map) ois.readObject();

ois.close();

return result;

}

private static ObjectInputStream getInputStream(Object src) throws IOException, ClassNotFoundException {

//写入字节流

ByteArrayOutputStream out = new ByteArrayOutputStream();

ObjectOutputStream obs = new ObjectOutputStream(out);

obs.writeObject(src);

obs.close();

//分配内存，写入原始对象，生成新对象

ByteArrayInputStream ios = new ByteArrayInputStream(out.toByteArray());

return new ObjectInputStream(ios);

}

}

结果：

====== DeepCopy Map =======

init: one: {one=fish}

init: two: {one=fish}

====== change to snake =======

change: one: {one=fish}

change: two: {one=snake}

总结：

在使用Map复制的时候，一般用第一种的方式，如果大量使用，也可以考虑用第三种方式。