https://github.com/google/guava/guava: Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more. 
/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.io;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.IOException;


A callback interface to process bytes from a stream.

processBytes will be called for each chunk of data that is read, and should return false when you want to stop processing. 
Author:Chris Nokleberg
Since:1.0
/**
 * A callback interface to process bytes from a stream.
 *
 * <p>{@link #processBytes} will be called for each chunk of data that is read, and should return
 * {@code false} when you want to stop processing.
 *
 * @author Chris Nokleberg
 * @since 1.0
 */
@Beta
@GwtIncompatible
public interface ByteProcessor<T> {
  
This method will be called for each chunk of bytes in an input stream. The implementation should process the bytes from buf[off] through buf[off + len - 1] (inclusive). 
Params:
  • buf – the byte array containing the data to process
  • off – the initial offset into the array
  • len – the length of data to be processed
Returns:true to continue processing, false to stop
/**
   * This method will be called for each chunk of bytes in an input stream. The implementation
   * should process the bytes from {@code buf[off]} through {@code buf[off + len - 1]} (inclusive).
   *
   * @param buf the byte array containing the data to process
   * @param off the initial offset into the array
   * @param len the length of data to be processed
   * @return true to continue processing, false to stop
   */
  @CanIgnoreReturnValue // some uses know that their processor never returns false
  boolean processBytes(byte[] buf, int off, int len) throws IOException;

  
Return the result of processing all the bytes. 
/** Return the result of processing all the bytes. */
  T getResult();
}