Find String hash collisions.

StringHash2.java

import java.util.*;
import java.io.*;

/**
 * Find String hash collisions.
 * @author Jesper Öqvist <[email protected]>
 */
public class StringHash2 {
	public static void main(String[] args) {
		Map<Integer,Collection<String>> map = new HashMap<>();
		Scanner scanner = new Scanner(System.in);
		int numLines = 0;
		while (scanner.hasNextLine()) {
			String line = scanner.nextLine();
			numLines += 1;
			int hash = line.hashCode();
			Collection<String> lines = map.get(hash);
			if (lines == null) {
				lines = new LinkedList<String>();
				lines.add(line);
				map.put(hash, lines);
			} else {
				lines.add(line);
			}
		}
		for (Map.Entry<Integer,Collection<String>> group : map.entrySet()) {
			Collection<String> lines = group.getValue();
			if (lines.size() > 1) {
				System.out.println("" + group.getKey() + ":");
				for (String line: lines) {
					System.out.println("\t" + line);
				}
			}
		}
		System.out.println("Num hash codes: " + map.keySet().size());
		System.out.println("Num lines: " + numLines);
	}
}