Creating a writable hashtable:

public class SymbolTable extends Hashtable implements Serializable
{
     
}
   
Delete/Add to the hash table (assuming name is the key):
    
        symbolTable.remove(sb.name);
        symbolTable.put(sb.name,sb);


For going through the hash table:

        Enumeration k = symbolTable.keys();
        while(k.hasMoreElements())
        {
            Symbol sb = (Symbol)symbolTable.get(k.nextElement());
            System.out.println(sb.name + " = " + sb.value);
        }
Quiz: Write a class called Quiz7, Symbol, SymbolTable.
getInput(String fileName)
From standard input read expressions such as
Pi = 3.1415926
e = 2.718
x = 56.43
Put the symbols in SymbolTable.
Write the entire SymbolTable to a file.

PrintTable(String fileName)
Read the entire symbol table from the file and
Print it out using Enumeration

For opening the files (you need to import java.awt.*):

  FileDialog openFileDialog =
	new FileDialog(this,"What file would you like to open?",
FileDialog.LOAD);
  openFileDialog.show();
     
    
    String fileName = openFileDialog.getFile();
    if(fileName==null)return;
    fileName = openFileDialog.getDirectory()+fileName;
    try{
        ObjectInputStream out = new ObjectInputStream(
        new FileInputStream(fileName));
        Writable loaded = new Writable();
        loaded = (Writable)out.readObject();
        System.out.println(loaded.x+" "+loaded.y);
        out.close();
        
    }catch(Exception x)
    { 
        System.err.println(x);
    }



For saving the files:

    FileDialog saveFileDialog = new FileDialog
    (this,"What file would you like to save to?",FileDialog.SAVE);
    
    saveFileDialog.show();
    
    String fileName = saveFileDialog.getFile();
    if(fileName==null)return;
    fileName = saveFileDialog.getDirectory()+fileName;
    
    try{
        ObjectOutputStream out = new ObjectOutputStream(
        new FileOutputStream(fileName));
        Writable test = new Writable();
        test.x = 45.89;
        test.y = 89.45;
        out.writeObject(test);
        out.close();
    }catch(IOException x)
    { 
        System.err.println(x);
    }