小波Note

        import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.stream.Collectors;

public class StreamExamples {

    public static void main(String[] args) {
        List<String> strings = Arrays.asList("apple", "banana", "cherry", "date", "elderberry", "fig", "grape");

        // 过滤：保留长度大于5的字符串
        List<String> filtered = strings.stream()
                .filter(s -> s.length() > 5)
                .collect(Collectors.toList());
        System.out.println("Filtered: " + filtered);

        // 映射：将所有字符串转换为大写
        List<String> mapped = strings.stream()
                .map(String::toUpperCase)
                .collect(Collectors.toList());
        System.out.println("Mapped: " + mapped);

        // 排序：按字母顺序排序
        List<String> sorted = strings.stream()
                .sorted()
                .collect(Collectors.toList());
        System.out.println("Sorted: " + sorted);

        // 统计：计算字符串的总长度
        int totalLength = strings.stream()
                .mapToInt(String::length)
                .sum();
        System.out.println("Total Length: " + totalLength);

        // 查找：找到第一个以字母 'c' 开头的字符串
        Optional<String> firstWithC = strings.stream()
                .filter(s -> s.startsWith("c"))
                .findFirst();
        firstWithC.ifPresent(s -> System.out.println("First with 'c': " + s));

        // 分组：按字符串长度分组
        Map<Integer, List<String>> groupedByLength = strings.stream()
                .collect(Collectors.groupingBy(String::length));
        System.out.println("Grouped by Length: " + groupedByLength);

        // 连接：将所有字符串连接成一个字符串，使用逗号分隔
        String joined = strings.stream()
                .collect(Collectors.joining(", "));
        System.out.println("Joined: " + joined);

        // 去重：去除重复的字符串
        List<String> distinct = strings.stream()
                .distinct()
                .collect(Collectors.toList());
        System.out.println("Distinct: " + distinct);

        // 限制：限制结果数量为3
        List<String> limited = strings.stream()
                .limit(3)
                .collect(Collectors.toList());
        System.out.println("Limited: " + limited);

        // 跳过：跳过前3个元素
        List<String> skipped = strings.stream()
                .skip(3)
                .collect(Collectors.toList());
        System.out.println("Skipped: " + skipped);
    }
}