以便将基元值数组转换为集合;这些值需要被boxed转换为相应的对象类型，或者需要调用原语流的collect方法。
拳击
下面是8个基本类型及其相应的 Package 类：

• bool → Boolean
• byte → Byte
• char → Character
• double → Double
• float → Float
• int → Integer
• long → Long
• short → Short
• 另请参阅 *：https://docs.oracle.com/javase/tutorial/java/data/autoboxing.html

在下面的代码中，int[]转换为IntStream，然后将其装箱到Stream<Integer>中，并使用Collectors.toMap收集器进行收集。

import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class PrimitiveStreamCollection {
    private static final String[] words = {
        "zero", "one", "two", "three", "four",
        "five", "six", "seven", "eight", "nine"
    };

    private static final int[] numbers = { 8, 6, 7, 5, 3, 0, 9 };

    public static Map<Integer, String> collectBoxed(int[] values) {
        return Arrays.stream(values)
            .boxed()
            .collect(
                Collectors.toMap(
                    Function.identity(),
                    value -> words[value]));
    }

    public static void main(String[] args) {
        Map<Integer, String> boxedMap = collectBoxed(numbers);
        System.out.println(boxedMap);
    }
}

原始流

Arrays.stream方法已被覆写，只接受double、int和long的数组。

• double[] → DoubleStream
• int[] → IntStream
• long[] → LongStream

在下面的代码中，collect方法是直接在原语流对象上调用的，它有三个参数：

• supplier-在本例中为HashMap<Integer, String>
• accumulator-如何将iteree应用于供应商
• combiner-如何组合多个值

import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class PrimitiveStreamCollection {
    private static final String[] words = {
        "zero", "one", "two", "three", "four",
        "five", "six", "seven", "eight", "nine"
    };

    private static final int[] numbers = { 8, 6, 7, 5, 3, 0, 9 };

    public static Map<Integer, String> collectUnboxed(int[] values) {
        return Arrays.stream(values)
            .collect(
                HashMap::new,
                (acc, value) -> acc.put(value, words[value]),
                HashMap::putAll);
    }

    public static void main(String[] args) {
        Map<Integer, String> unboxedMap = collectUnboxed(numbers);
        System.out.println(unboxedMap);
    }
}