Here you can find the source of copyLarge(Reader input, Writer output)
public static long copyLarge(Reader input, Writer output) throws IOException
//package com.java2s; //License from project: Apache License import java.io.*; public class Main { public static long copyLarge(Reader input, Writer output) throws IOException { char[] buffer = new char[4096]; long count = 0L; int n1;/* w w w. j a v a 2s .com*/ for (; -1 != (n1 = input.read(buffer)); count += (long) n1) { output.write(buffer, 0, n1); } return count; } }