//Stream通用语法:创建Stream + 转换Stream + 聚合， 例如： nums.stream().filter(num -> num != null).count();

//1，转换

//1-1, distinct

//1-2, filter

//1-3, map

//1-4, flatMap

//1-5, peek

//1-6, limit

//1-7, skip

//2, 聚合

//2-1, collect

//2-2, sum

//2-3, count

//2-4, max/min

public static void main(String[] args) {

List<Integer> nums = new ArrayList<>(Arrays.asList(1, 1, 1, 1, 1, null, 3, 4, null, 6));

Stream.distinct(nums);

Stream.filter(nums);

Stream.map(nums);

Stream.collect2Map(nums);

Stream.collect2Set(nums);

}

//1, distinct

public static void distinct(List<Integer> nums) {

List<Integer> collect = nums.stream().distinct().collect(Collectors.toList());

System.out.println(collect);

}

//2, filter

public static void filter(List<Integer> nums) {

List<Integer> collect = nums.stream().filter(Objects::nonNull).collect(Collectors.toList());

System.out.println(collect);

}

//3, map

public static void map(List<Integer> nums) {

Set<String> collect = nums.stream().map(String::valueOf).collect(Collectors.toSet());

System.out.println(collect); //[1, 3, null, 4, 6]

}

//4-1. collect.toMap ,注意，如果不去重，则当新增的key-value相同时会报错

public static void collect2Map(List<Integer> nums){

Map<String, Double> collect = nums.stream().map(String::valueOf).distinct().collect(Collectors.toMap(s -> s, s -> Math.random()));

System.out.println(collect);

}

//4-2. collect.toSet

public static void collect2Set(List<Integer> nums){

Set<String> collect = nums.stream().map(String::valueOf).collect(Collectors.toSet());

System.out.println(collect);

}

//4-3. collect.toList

public static void collect2List(List<Integer> nums){

List<String> collect = nums.stream().map(String::valueOf).collect(Collectors.toList());

System.out.println(collect);

}

}