C# 与 JAVA 常见代码对照表

#	功能表述	JAVA	C#	差异点
1	新建List	List list =Lists.newArrayList(); List list =Lists.newLinkedList();	List list = new List();	在C#中，List只有一种实现，即List java则有多种
2	新建Map	Map map = Maps.newHashMap();	Dictionary dict = new Dictionary();	在C#中，Map使用Dictionary来实现, java则有多种
3	循环List	for (String s : list) {     System.out.println(s); }	foreach (string s in list) {     Console.WriteLine(s); }
4	循环Map	for (Map.Entry entry : map.entrySet()) {     System.out.println(entry.getKey() + ": " + entry.getValue()); }	foreach (KeyValuePair kvp in dict) {     Console.WriteLine(kvp.Key + ": " + kvp.Value); }
5	foreach	list.forEach(item -> System.out.println(item));	list.ForEach(item => Console.WriteLine(item));
6	以对象的某个属性为key,另一属性为value,转Map	Map map = peopleList.stream()     .collect(Collectors.toMap(Person::getName, Person::getAge));	Dictionary map = peopleList.ToDictionary(t => t.Name,t => t.Age);	java:  key重复,后来者取而代之 c#: 报错
7	以对象的某个属性为key,自身为value,转Map	Map map = peopleList.stream()     .collect(Collectors.toMap(Person::getName, Function.identity()));	Dictionary map= peopleList.ToDictionary(t => t.Name);	java:  key重复,后来者取而代之 c#: 报错
8	给对象中某属性重新赋值	peopleList.stream()     .map(person ->  { person.setAge(person.getAge() + 10);         return person; })     .collect(Collectors.toList());	peopleList= peopleList.Select(                 person => {                         x.age= x.age + 10;                         return person;                 }).ToList();
9	对对象列表以某条件进行过滤	List result = list.stream()     .filter(i -> i % 2 == 0)     .collect(Collectors.toList());	List result = list.Where(i => i % 2 == 0).ToList();
10	对对象列表进行分组并转为Map	Map> ageGroups = persons.stream()     .collect(Collectors.groupingBy(Person::getAge));	Dictionary> map ageGroups = persons.GroupBy(p => p.Age).ToDictionary(g => g.Key, g => g.ToList());
11	对对象列表根据某属性进行排序	List sortedPersons = persons.stream() .sorted(Comparator.comparing(Person::getAge))     .collect(Collectors.toList());	ListsortedPersons = persons.OrderBy(p => p.Age);
12	对对象列表根据某属性去重	List distinctPersons = persons.stream().collect(         Collectors.collectingAndThen(                 Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(Person::getId))),                 ArrayList::new));	var distinctPersons = persons.GroupBy(p => p.Id).Select(g => g.First()).ToList();