First non-repeating character in a string

FirstNonRepeating

package practice;

import java.util.Scanner;

public class Solution1 {
	
	//first non-repeating character in a string
	
	private static int[] buildFreq(String str){
		
		int freq[] = new int[26];
		for(int i = 0; i<26; i++){
			freq[i] = 0;
		}
		//build freq[]
		for(int i = 0; i<str.length(); i++){
			freq[str.charAt(i) - 'a']++;
		}
		return freq;
	}
	
	private static char solve(String str){
		
		int freq[] = new int[26];
		freq = buildFreq(str);
		for(int i = 0; i<26; i++){
			if(freq[str.charAt(i) - 'a'] == 1){
				return str.charAt(i);
			}
		}
		return ' ';
	}

	public static void main(String[] args) {
		
		Scanner s = new Scanner(System.in);
		int test = s.nextInt();
		s.nextLine();
		while(test > 0){
			String str = s.nextLine();
			System.out.println(solve(str));
			test--;
		}
		s.close();
	}

}