ByteArrayInputStream class

ByteArrayInputStream is an implementation of an InputStream that uses a byte array as the source.

This class has two constructors, each of which requires a byte array to provide the data source:

ByteArrayInputStream(byte array[ ]): array is the input source.
ByteArrayInputStream(byte array[ ], int start, int numBytes): uses a subset of your byte array.

Methods from ByteArrayInputStream

int available(): Returns the number of remaining bytes that can be read (or skipped over) from this input stream.
void close(): Closing a ByteArrayInputStream has no effect.
void mark(int readAheadLimit): Set the current marked position in the stream.
boolean markSupported(): If this InputStream supports mark/reset.
int read(): Reads the next byte of data.
int read(byte[] b, int off, int len): Reads up to len bytes of data into an array of bytes from this input stream.
void reset(): Resets the buffer to the marked position.
long skip(long n): Skips n bytes of input from this input stream.

Revised from Open JDK source code

Create ByteArrayInputStream from byte array


import java.io.ByteArrayInputStream;
import java.io.IOException;

public class Main {
  public static void main(String args[]) throws IOException {
    String tmp = "abcdefghijklmnopqrstuvwxyz";
    byte b[] = tmp.getBytes();
    ByteArrayInputStream input1 = new ByteArrayInputStream(b);
    ByteArrayInputStream input2 = new ByteArrayInputStream(b, 0, 3);
  }
}

A ByteArrayInputStream implements both mark( ) and reset( ). The following example uses the reset( ) method to read the same input twice.

 
import java.io.ByteArrayInputStream;
import java.io.IOException;

public class Main {
  public static void main(String args[]) throws IOException {
    String tmp = "abc";
    byte b[] = tmp.getBytes();
    ByteArrayInputStream in = new ByteArrayInputStream(b);
    for (int i = 0; i < 2; i++) {
      int c;
      while ((c = in.read()) != -1) {
        if (i == 0) {
          System.out.print((char) c);
        } else {
          System.out.print(Character.toUpperCase((char) c));
        }
      }
      System.out.println();
      in.reset();

    }
  }
}

The following code reads byte array out of ByteArrayInputStream


import java.io.ByteArrayInputStream;
import java.io.IOException;

public class Main {
  public static void main(String args[]) throws IOException {
    ByteArrayInputStream inStream = new ByteArrayInputStream(("java2s.com").getBytes());
    int inBytes = inStream.available();
    System.out.println("inStream has " + inBytes + " available bytes");
    byte inBuf[] = new byte[inBytes];
    int bytesRead = inStream.read(inBuf, 0, inBytes);
    System.out.println(bytesRead + " bytes were read");
    System.out.println("They are: " + new String(inBuf));
  }
}

The output:


inStream has 10 available bytes
10 bytes were read
They are: java2s.com

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