Java中实现Map和List对象的文件存储技术详解

java的IO包当中提供了&＃xff0c;向文件中写入文件和读取文件的方法。好吧&＃xff0c;来看下具体怎么回事吧。我们先写一个像文件当中写单个对象的方法吧。

public void writeObject() {

try {

HashMap map &＃61; new HashMap();

map.put("name", "foolfish");

FileOutputStream outStream &＃61; new FileOutputStream("E:/1.txt");

ObjectOutputStream objectOutputStream &＃61; new ObjectOutputStream(outStream);

objectOutputStream.writeObject(map);

outStream.close();

System.out.println("successful");

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

这里我们将一个map对象插入一个txt文件当中。java的IO包当中提供了Object的文件流。代码很简单&＃xff0c;我们下面来看一看从该文件当中读取这个对象吧

public void readObject(){

FileInputStream freader;

try {

freader &＃61; new FileInputStream("E:/1.txt");

ObjectInputStream objectInputStream &＃61; new ObjectInputStream(freader);

HashMap map &＃61; new HashMap();

map &＃61; (HashMap) objectInputStream.readObject();

System.out.println("The name is " &＃43; map.get("name"));

} catch (FileNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

代码也很简单&＃xff0c;我们使用ObjectInputStream 的readobject的就可以读取文件中的对象&＃xff0c;再按照封装对

象时候的类型进行强制转换一下。输出结果是aa foolfish。

上面提供的是对单个对象的存入和读取。对多个不同的对象该方法也适用。还是用代码来说明下吧。我们同时插入两个不同的对象&＃xff0c;一个map&＃xff0c;一个list。

public class ObjectToFile {

public void writeObject() {

try {

HashMap map &＃61; new HashMap();

map.put("name", "foolfish");

List list &＃61; new ArrayList();

list.add("hello");

list.add("everyone");

FileOutputStream outStream &＃61; new FileOutputStream("E:/1.txt");

ObjectOutputStream objectOutputStream &＃61; new ObjectOutputStream(outStream);

objectOutputStream.writeObject(map);

objectOutputStream.writeObject(list);

outStream.close();

System.out.println("successful");

} catch (FileNotFoundException e) {

e.printStackTrace();

} catch (IOException e) {

e.printStackTrace();

}

}

public void readObject(){

FileInputStream freader;

try {

freader &＃61; new FileInputStream("E:/1.txt");

ObjectInputStream objectInputStream &＃61; new ObjectInputStream(freader);

HashMap map &＃61; new HashMap();

map &＃61; (HashMap) objectInputStream.readObject();

ArrayList list &＃61; new ArrayList();

list &＃61; (ArrayList) objectInputStream.readObject();

System.out.println("The name is " &＃43; map.get("name"));

System.out.println("aa " &＃43; list.get(1));

} catch (FileNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

public static void main(String args[]){

ObjectToFile of &＃61; new ObjectToFile();

of.writeObject();

of.readObject();

}

}