Java ways to save objects to a file/read objects from a file _java

1. Save the object to the file

The Java language can only save objects for classes that implement the serializable interface to a file, using the following methods:

public static void Writeobjecttofile (Object obj)
  {
    file file =new file ("Test.dat");
    FileOutputStream out;
    try {out
      = new FileOutputStream (file);
      ObjectOutputStream objout=new ObjectOutputStream (out);
      Objout.writeobject (obj);
      Objout.flush ();
      Objout.close ();
      System.out.println ("Write Object success!");
    } catch (IOException e) {
      System.out.println ("Write object Failed");
      E.printstacktrace ();
    }
  

Parameter obj must implement the Serializable interface, otherwise it throws a Java.io.NotSerializableException exception. In addition, if the object being written is a container, such as list, MAP, also ensure that each element in the container implements the serializable interface. For example, if you declare a hashmap as follows and call the Writeobjecttofile method, an exception is thrown. But if it is hashmap<string,string>, it will not go wrong because the String class has implemented the serializable interface. In addition, if the inherited base class does not implement serializable if it is a class created by itself, the class needs to implement serializable, or it cannot be written to the file in this way.

Object Obj=new object ();
    Failed,the object in map does not implement Serializable interface hashmap<string
    , object> objmap=new <String,Object> ();
    Objmap.put ("Test", obj);
    Writeobjecttofile (OBJMAP);

2. Reading objects from files

You can read objects from a file using the following methods

public static Object Readobjectfromfile ()
  {
    object temp=null;
    File file =new file ("Test.dat");
    FileInputStream in;
    try {in
      = new FileInputStream (file);
      ObjectInputStream objin=new ObjectInputStream (in);
      Temp=objin.readobject ();
      Objin.close ();
      System.out.println ("read Object success!");
    } catch (IOException e) {
      System.out.println ("read object failed");
      E.printstacktrace ();
    } catch (ClassNotFoundException e) {
      e.printstacktrace ();
    }
    return temp;
  }

After the object is read, it is converted based on the actual type of the object.

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