java构建Stream流的多种方式总结

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

int sum = numbers.stream()
                .filter(n -> n % 2 == 0) // 过滤偶数
                .map(n -> n * 2) // 将偶数翻倍
                .reduce(0, Integer::sum); // 求和

System.out.println("偶数的翻倍之和为: " + sum);

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Stream;

public class StreamCreationExample {

    public static void main(String[] args) {
        List<String> names = new ArrayList<>();
        names.add("Alice");
        names.add("Bob");
        names.add("Charlie");
        names.add("David");
        names.add("Eve");

        // 创建一个Stream流
        Stream<String> nameStream = names.stream();

        // 使用Stream流进行操作
        nameStream
            .filter(name -> name.startsWith("A"))
            .forEach(System.out::println);
    }
}

import java.util.HashMap;
import java.util.Map;
import java.util.stream.Stream;

public class StreamCreationFromMapExample {

    public static void main(String[] args) {
        Map<Integer, String> studentMap = new HashMap<>();
        studentMap.put(1, "Alice");
        studentMap.put(2, "Bob");
        studentMap.put(3, "Charlie");
        studentMap.put(4, "David");
        studentMap.put(5, "Eve");

        // 从Map的键集合创建Stream
        Stream<Integer> studentIdsStream = studentMap.keySet().stream();

        // 使用Stream流进行操作
        studentIdsStream
            .filter(id -> id % 2 == 0)
            .forEach(id -> System.out.println(id + ": " + studentMap.get(id)));
    }
}

import java.util.Arrays;
import java.util.stream.IntStream;

public class StreamCreationFromArrayExample {

    public static void main(String[] args) {
        int[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

        // 从整数数组创建IntStream
        IntStream numberStream = Arrays.stream(numbers);

        // 使用Stream流进行操作
        int sum = numberStream
            .filter(n -> n % 2 == 0)
            .map(n -> n * 2)
            .sum();

        System.out.println("偶数的翻倍之和为: " + sum);
    }
}

import java.util.Arrays;
import java.util.stream.Stream;

public class StreamCreationFromArrayExample {

    public static void main(String[] args) {
        String[] words = {"apple", "banana", "cherry", "date", "elderberry"};

        // 从字符串数组创建Stream
        Stream<String> wordStream = Arrays.stream(words);

        // 使用Stream流进行操作
        wordStream
            .filter(word -> word.startsWith("b"))
            .map(String::toUpperCase)
            .forEach(System.out::println);
    }
}

import java.util.stream.Stream;

public class StreamFactoryExample {

    public static void main(String[] args) {
        // 使用Stream.of创建Stream流
        Stream<String> stream = Stream.of("Apple", "Banana", "Cherry", "Date");

        // 打印Stream中的元素
        stream.forEach(System.out::println);
    }
}

import java.util.Random;
import java.util.stream.Stream;

public class StreamGenerateExample {

    public static void main(String[] args) {
        // 使用Stream.generate创建随机整数流
        Stream<Integer> randomIntStream = Stream.generate(() -> new Random().nextInt(100));

        // 限制流的元素数量，然后打印
        randomIntStream
            .limit(10)
            .forEach(System.out::println);
    }
}

import java.util.stream.Stream;

public class StreamBuilderExample {

    public static void main(String[] args) {
        Stream.Builder<Integer> builder = Stream.builder();

        // 添加元素到Stream
        for (int i = 1; i <= 10; i++) {
            builder.accept(i);
        }

        // 构建Stream
        Stream<Integer> numberStream = builder.build();

        // 使用Stream操作
        numberStream
            .filter(n -> n % 2 == 0) // 过滤偶数
            .forEach(System.out::println);
    }
}

import java.util.stream.Stream;

public class FibonacciStreamExample {

    public static void main(String[] args) {
        Stream.Builder<Long> builder = Stream.builder();

        long a = 0, b = 1;
        int count = 10;

        for (int i = 0; i < count; i++) {
            builder.accept(a);
            long next = a + b;
            a = b;
            b = next;
        }

        Stream<Long> fibonacciStream = builder.build();

        fibonacciStream.forEach(System.out::println);
    }
}

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Stream;

public class FileToStreamExample {

    public static void main(String[] args) {
        String filePath = "sample.txt"; // 文件路径

        try (Stream<String> lines = Files.lines(Paths.get(filePath))) {
            lines.forEach(System.out::println); // 逐行打印文件内容
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.stream.Stream;

public class BinaryFileToStreamExample {

    public static void main(String[] args) {
        String filePath = "image.jpg"; // 二进制文件路径

        try {
            Path path = Paths.get(filePath);
            Stream<Byte> byteStream = Files.newInputStream(path)
                                          .map(b -> (byte) b);

            byteStream.forEach(System.out::println); // 逐字节打印二进制文件内容
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}