Reading a binary input stream into a single byte array in Java

Question

The documentation says that one should not use available() method to determine the size of an InputStream. How can I read the whole content of an <

Answer 1

Please keep in mind that the answers here assume that the length of the file is less than or equal to Integer.MAX_VALUE(2147483647).

If you are reading in from a file, you can do something like this:

    File file = new File("myFile");
    byte[] fileData = new byte[(int) file.length()];
    DataInputStream dis = new DataInputStream(new FileInputStream(file));
    dis.readFully(fileData);
    dis.close();

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UPDATE (May 31, 2014):

Java 7 adds some new features in the java.nio.file package that can be used to make this example a few lines shorter. See the readAllBytes() method in the java.nio.file.Files class. Here is a short example:

import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;

// ...
        Path p = FileSystems.getDefault().getPath("", "myFile");
        byte [] fileData = Files.readAllBytes(p);

Android has support for this starting in Api level 26 (8.0.0, Oreo).