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<String,String> map = new HashMap<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<String,String> map = new HashMap<String,String>();
map = (HashMap<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<String,String> map = new HashMap<String,String>();
map.put("name", "foolfish");

List<String> list = new ArrayList<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<String,String> map = new HashMap<String,String>();
map = (HashMap<String, String>) objectInputStream.readObject();
ArrayList<String> list = new ArrayList<String>();
list = (ArrayList<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();
}
}