IsUnique.java

//http://coolcodebro.blogspot.com/2012/12/determine-if-string-has-all-unique.html

public class IsUnique {
	public static void main(String[] args) {
		new IsUnique().run();
	}
	
	void run() {
		String str = "123456789a0";
		
		System.out.println("String: " + str);
		System.out.println("Using hashmap: " + hasAllUnique(str));
		System.out.println("Using array: " + hasAllUnique1(str));
		
		System.out.println();
		
		str = "AbCcdefbz";
		System.out.println("String: " + str);
		System.out.println("Using hashmap: " + hasAllUnique(str));
		System.out.println("Using array: " + hasAllUnique1(str));		
	}
	
	//Using map
	boolean hasAllUnique(String str) {
		Map<Character, Integer> map = new HashMap<Character, Integer>();
		
		for(int i=0; i<str.length(); i++) {
			char currChar = str.charAt(i);
			
			if(map.get(currChar) == null)
				map.put(currChar, 1);
			else
				return false;
		}
		
		return true;
	}
	
	//Using arrays. Assumption: all characters are ASCII
	boolean hasAllUnique1(String str) {
		boolean[] taken = new boolean[256];
		
		for(int i=0; i<str.length(); i++) {
			int index = (int) str.charAt(i);
			
			if(taken[index])
				return false;
			
			taken[index] = true;
		}
		
		return true;
	}
}