java中将list、map对象写入文件

java的IO包当中提供了，向文件中写入文件和读取文件的方法。好吧，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<</span>String,String> map = new HashMap<</span>String,String>();

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

FileOutputStream outStream = new FileOutputStream("E:/1.txt");

ObjectOutputStream objectOutputStream = 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，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 = new FileInputStream("E:/1.txt");

ObjectInputStream objectInputStream = new ObjectInputStream(freader);

HashMap<</span>String,String> map = new HashMap<</span>String,String>();

map = (HashMap<</span>String, String>) objectInputStream.readObject();

System.out.println("The name is " + 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，我们使用ObjectInputStream的readobject的就可以读取文件中的对象，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，一个map，一个list。

public class ObjectToFile {

public void writeObject() {

try {

HashMap<</span>String,String> map = new HashMap<</span>String,String>();

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

List<</span>String> list = new ArrayList<</span>String>();

list.add("hello");

list.add("everyone");

FileOutputStream outStream = new FileOutputStream("E:/1.txt");

ObjectOutputStream objectOutputStream = 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 = new FileInputStream("E:/1.txt");

ObjectInputStream objectInputStream = new ObjectInputStream(freader);

HashMap<</span>String,String> map = new HashMap<</span>String,String>();

map = (HashMap<</span>String, String>) objectInputStream.readObject();

ArrayList<</span>String> list = new ArrayList<</span>String>();

list = (ArrayList<</span>String>) objectInputStream.readObject();

System.out.println("The name is " + map.get("name"));

System.out.println("aa " + 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 = new ObjectToFile();

of.writeObject();

of.readObject();

}

}