算法題:統計第一次出現的字符

(1)方法1
使用HashSet

public void test1() {
		Map<Character, Integer> map=new HashMap<Character, Integer>();
		String str ="asgasdgdshhffmddjjnan";
		Character c =null;
		for (int i = 0; i < str.length(); i++) {
			Character character=str.charAt(i);
			Integer count = map.get(character);
			if (count==null) {
				map.put(character,1);
			} else {
				map.put(character,1+count);
			}
		}
		for(Character key:map.keySet()) {
			if (map.get(key)==1) {
				c=key;
				
				break;
			}
		}
		System.out.println(c);
	}

(2)方法2
使用字符串的indexOf和lastIndexOf方法

	public void test2() {
		String str ="asgasdgdshhffmddjjnan";
		Character c =null;
		
		for (int i = 0; i < str.length(); i++) {
			char character=str.charAt(i);
			if (str.indexOf(character)==str.lastIndexOf(character)) {
				c = character;
				break;
			}
		}
		System.out.println(c);
	}