java集合List快速实现重复判断的方法小结

import java.util.Arrays;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;

public class CheckDuplicate {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("A", "B", "C", "A");

        // 找到重复元素
        Set<String> duplicates = list.stream()
                .filter(item -> list.stream().filter(item::equals).count() > 1)
                .collect(Collectors.toSet());

        System.out.println("重复元素: " + duplicates);
        System.out.println("是否存在重复数据: " + !duplicates.isEmpty());
    }
}

import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class CheckDuplicate {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("A", "B", "C", "A");

        Set<String> seen = new HashSet<>();
        boolean hasDuplicate = list.stream().anyMatch(item -> !seen.add(item));

        System.out.println("是否存在重复数据: " + hasDuplicate);
    }
}

import cn.hutool.core.collection.CollUtil;

import java.util.Arrays;
import java.util.List;
import java.util.Set;

public class CheckDuplicate {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("A", "B", "C", "A");

        // 使用 Hutool 的工具方法创建 HashSet
        Set<String> set = new HashSet<>(list);
        boolean hasDuplicate = set.size() != list.size();

        System.out.println("是否存在重复数据: " + hasDuplicate);
    }
}

import cn.hutool.core.collection.CollUtil;

import java.util.Arrays;
import java.util.List;
import java.util.Map;

public class CheckDuplicate {
    public static void main(String[] args) {
        List<String> list = Arrays.asList("A", "B", "C", "A", "B");

        // 统计每个元素出现的次数
        Map<String, Integer> countMap = CollUtil.countMap(list);
        
        // 打印重复元素
        countMap.forEach((key, value) -> {
            if (value > 1) {
                System.out.println("重复元素: " + key + "，出现次数: " + value);
            }
        });
    }
}