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public class Streams {		private static List
   
     list = new ArrayList
    
     ();		public static void main(String[] args) {		list =  Arrays.asList(				new User(1, "a", 10),				new User(4, "d", 19),				new User(5, "e", 13),				new User(2, "b", 14),				new User(3, "a", 10),				new User(6, "f", 16)				);				long start = System.currentTimeMillis();				order();				println(String.format("耗时[%s]毫秒", (System.currentTimeMillis() - start)));			}		/**	 * 多条件去重	 * @param list	 */	public static void order() {		list.stream().collect(Collectors.collectingAndThen(				Collectors.toCollection(() -> new TreeSet<>(						Comparator.comparing(o -> o.getAge() + ";" + o.getName()))), ArrayList::new)).forEach(u -> println(u));	}		public static void group() {		Map
     
      > collect = list.stream().collect(Collectors.groupingBy(User::getAge));		System.out.println(collect);	}		/**	 * filter过滤	 * @param list	 */	public static void filterAge() {		list.stream().filter(u -> u.getAge() == 10).forEach(u -> println(u));	}		/**	 * sorted排序	 */	public static void stord() {		list.stream().sorted(Comparator.comparing(u-> u.getAge())).forEach(u -> println(u));			}	/**	 * limit方法限制最多返回多少元素	 */	public static void limit() {		list.stream().limit(2).forEach(u -> println(u));	}	/**	 * 不要前多n个元素，n大于满足条件的元素个数就返回空的流	 */	public static void skip() {		list.stream().skip(2).forEach(u -> println(u));	}	// 最大值 最小值	public static void statistics() {		Optional
      
        min = list.stream().min(Comparator.comparing(User::getUserId));		println(min);		Optional
       
         max = list.stream().max(Comparator.comparing(User::getUserId));		println(max);	}		// 统计	public static void summarizingInt(){		IntSummaryStatistics statistics = list.stream().collect(Collectors.summarizingInt(User::getAge));		double average = statistics.getAverage();		long count = statistics.getCount();		int max = statistics.getMax();		int min = statistics.getMin();		long sum = statistics.getSum();		println(average);		println(count);		println(min);		println(sum);		println(max);			}	/**	 * 转set	 */	public static void toSet() {		Set
        
          collect = list.stream().collect(Collectors.toSet()); Iterator
         
           iterator = collect.iterator(); while(iterator.hasNext()) { System.out.println(iterator.next().getUserId()); } } /** * 转map */ public static void toMap() { Map
          
            collect = list.stream().collect(Collectors.toMap(User::getUserId, u -> u)); for (Integer in : collect.keySet()) { User u = collect.get(in);//得到每个key多对用value的值 println(u); } } /** *map */ public static void map() { list.stream().map(User::getUserId).forEach(userId -> println(userId)); list.stream().mapToInt(User::getAge).forEach(userId -> println(userId)); list.stream().mapToDouble(User::getUserId).forEach(userId -> println(userId)); list.stream().mapToLong(User::getUserId).forEach(userId -> println(userId)); } /** * 查找与匹配 * allMatch方法与anyMatch差不多，表示所有的元素都满足才返回true。noneMatch方法表示没有元素满足 */ public static void anyMatch() { boolean anyMatch = list.stream().anyMatch(u -> u.getAge() == 100); boolean allMatch = list.stream().allMatch(u -> u.getUserId() == 10); boolean noneMatch = list.stream().noneMatch(u -> u.getUserId() == 10); println(anyMatch); println(allMatch); println(noneMatch); } /** * reduce操作 */ public static void reduce() { Optional
           
             sum = list.stream().map(User::getAge).reduce(Integer::sum); Optional
            
              max = list.stream().map(User::getAge).reduce(Integer::max); Optional
             
               min = list.stream().map(User::getAge).reduce(Integer::min); println(sum); println(max); println(min); } /** * 公共输出 * @param c */ public static void println(Object c) { System.out.println(c.toString()); } static class User { private Integer userId; private String name; private Integer age; User(Integer userId, String name, Integer age) { super(); this.userId = userId; this.name = name; this.age = age; } public Integer getUserId() { return userId; } public void setUserId(Integer userId) { this.userId = userId; } public String getName() { return this.name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } @Override public String toString() { return "[userId=" + userId + ", name=" + name + ", age=" + age + "]"; } }
             
            
           
          
         
        
       
      
     
    
   

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