异或的应用场景：以O(N)时间复杂度查找文章中出现了奇数次的字符串

import com.google.common.base.Splitter;
import org.apache.commons.lang.RandomStringUtils;

import java.util.List;

/**
 * Created by kongzheng on 16/3/31.
 */
public class Finder {

    public static void main(String[] args) throws Exception {
        final String SEEDS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

        StringBuilder buf = new StringBuilder();
        for (int i = 0; i < 100000; i++) {
            String eventStr = "A" + RandomStringUtils.random(19, SEEDS);
            buf.append(eventStr).append(" ");
            buf.append(eventStr).append(" ");

        }
        String oddStr = "B" + RandomStringUtils.random(19, SEEDS);
        System.out.println(oddStr);
        buf.append(oddStr).append(" ");

        List<String> list = Splitter.on(‘ ‘).omitEmptyStrings().trimResults().splitToList(buf.toString());
        byte[] array0 = list.get(0).getBytes();
        for (int i = 1; i < list.size(); i++) {
            byte[] arrayi = list.get(i).getBytes();
            array0 = xor(array0, arrayi);
        }
        System.out.println(new String(array0));
    }

    private static byte[] xor(byte[] array1, byte[] array2) {
        byte[] buf = new byte[Math.max(array1.length, array2.length)];
        for (int i = 0; i < buf.length; i++) {
            byte b1 = i < array1.length ? array1[i] : 0;
            byte b2 = i < array2.length ? array2[i] : 0;
            buf[i] = (byte) (b1 ^ b2);
        }
        return buf;
    }

}