题解 | #找出字符串中第一个只出现一次的字符#

import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String text = sc.next();
        Map<Character, Integer> map = new LinkedHashMap<>();
        for (int i = 0; i < text.length(); i++) {
            char c = text.charAt(i);
            map.merge(c, 1, (oldVal, newVal) -> oldVal + 1);
        }
        for (Entry<Character, Integer> entry : map.entrySet()) {
            if (entry.getValue() == 1) {
                System.out.println(entry.getKey());
                return;
            }
        }
        System.out.println(-1);
    }
}