IO流读取文件内容时，出现空格的问题（未找到原因）

import java.io.File;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;

import java.util.Arrays;

public class TestFileWriter {

	public static void main(String[] args) throws IOException {

		File i = new File("D:\\Huang\\123.txt");

		FileReader r = new FileReader(i);

		FileWriter w = new FileWriter("D:\\Huang\\abcd.txt");

		StringBuilder sb = new StringBuilder();

		int b = -1;

		char[] cs = new char[(int) i.length()];

		int num = 0;

		System.out.println(i.length());

		while ((b = r.read(cs)) != -1) {

			sb.append(cs);

			System.out.println((num++) + Arrays.toString(cs));

			System.out.println((num++) + String.valueOf(cs));//打印输出时   会输出空格

		}

		w.write(sb.toString());

		w.flush();

		r.close();

		w.close();

	}