read from one file, modify it and write to new file in java, any one help me.. i'm new to java

// Reading File
		String fileName = "temp.txt";
		String NewfileName =  "New_temp.txt";
		String FileContent = "";
        String line = null;
        try 
		{
            FileReader fileReader = new FileReader(fileName);
            BufferedReader bufferedReader = new BufferedReader(fileReader);
			
		  
			while((line = bufferedReader.readLine()) != null) 
			{
				FileContent = line;
            } 
			
            bufferedReader.close();            
        }
        catch(IOException ex) 
		{
            System.out.println("Error reading file '" + fileName + "'" + ex.printStackTrace());                   
        }

// Changing Content of File
				// Do changes with  'FileContent' 
		
		
// Writeing in New  File
		try
		{
			FileWriter fileWriter =new FileWriter(NewfileName);
            BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
          
			bufferedWriter.write(FileContent);
			
			bufferedWriter.close();			
		}
        catch(IOException ex) 
		{
            System.out.println("Error Writing file '" + NewfileName + "'" + ex.printStackTrace());                   
        }