How to compare and add a line to a txt file?

Question

Java

Hello!
Maybe someone knows how to add a line to txt. Let me explain...
There is a zp.txt file, let's say in it:
Sasha 05/27/2015 1500
Masha 03/24/2015 2200
Igor 04/12/2015 3400
And all this is unloaded into a JTable from txt. I pay salaries to employees in the third column. But each date has its own price, since I'm not filling this table, I need to check the correctness by adding one more line for each date. To get it like this:
Sasha 05/27/2015 1500 1430
Masha 03/24/2015 2200 2200
Igor 04/12/2015 3400 3399
1430, 2200, 3399 - I enter from the keyboard, but you need to search for the line and add it by date.
PS Help guys, I'm not strong in java, I'll throw 100 rubles as a token of gratitude. to the phone.
Thanks in advance.