Inefficient OutputStream implementation JAVA-P1002

This class appears to inherit the write(byte[], int, int) method from java.io.OutputStream or java.io.FilterOutputStream, which renders it an inefficient implementation.

Always override write(byte[], int, int) suitably when inheriting from these types to avoid using an inefficient implementation.

The default implementation of the array based write methods in OutputStream and FilterOutputStream just call the write(int) method in a loop.

Taken from java.io.OutputStream's source code:

public void write(byte b[], int off, int len) throws IOException {
    Objects.checkFromIndexSize(off, len, b.length);
    // len == 0 condition implicitly handled by loop bounds
    for (int i = 0 ; i < len ; i++) {
        write(b[off + i]); // A straightforward loop...
    }
}

This is sub-optimal and will reduce write performance. Unless a custom OutputStream delegates the array write method to a more efficient implementation, or implements the method itself, it is likely that writing multiple bytes at once will be handled inefficiently.

Bad Practice

public class CustomOutputStream extends OutputStream {
    FileOutputStream underlyingImpl;

    @Override
    public void write(int b) {
        underlyingImpl.write(b);
    }

    // This class delegates the implementation of the array write method to its parent class...
}

Recommended

Make sure to override the array write method and either implement it efficiently, or pass on the data to a good implementation.

public class CustomOutputStream extends OutputStream {
    FileOutputStream underlyingImpl;

    @Override
    public void write(int b) {
        underlyingImpl.write(b);
    }

    @Override
    public void write(byte[] b, int off, int len) {
        // FileOutputStream efficiently implements this method.
        underlyingImpl.write(b, off, len);
    }

}

References

• Oracle Java 8 Javadocs - java.io.OutputStream.write(byte[] b, int off, int len)
• Oracle Java 8 Javadocs - java.io.FilterOutputStream.write(byte[] b, int off, int len)