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Lesson 11 - Binary Files in Java

In the previous exercise, Solved tasks for Java Files Lessons 6-10, we've practiced our knowledge from previous lessons.

In the last lesson, Solved tasks for Java Files Lessons 6-10, we focused on serialization and deserialization. Throughout this course, we've already mentioned several ways to store data (or instances if possible) into files. Whether it was the CSV or XML format, we have always technically worked with text files. In today's Java tutorial, we're going to introduce you to a different way of storing data and talk about its advantages and disadvantages.

Binary Files

So far, we always converted data types to strings and saved them to a text file. When we read the data back again, we had to parse it from the String back to the original data type. However, we aren't limited to storing data as text into files. Today, we'll go over storing data into binary files.

As you already know, variables are stored in the computer's RAM memory. Physically, we can imagine the memory as a really long line of "boxes" with either a zero or a one in each box. The individual elements in the boxes are bits. We usually don't work with bits individually but by 8 at a time. Sets of eight bits are known as bytes (1 byte = 8 bits). Each Java data type occupies a certain number of bytes in memory. For example, int occupies 4 (a total of 32 zeros and ones). It doesn't matter whether there is a value of 0 or 1,000,000 stored inside, it always has 4 bytes reserved in memory. If we need to store a variable of the int type in a file, we simply


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This Java tutorial introduces you to binary files and the DataOutputStream and DataInputStream classes. We'll learn to read and write instances in binary.

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Article has been written for you by Michal Čápka
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