JAVA8新方法（也不新啦，我们老啦） java8jdk8java

就记录在这吧，虽然这个名字叫JAVA8新方法，但是实际上JAVA8一点也不新啦，主要是我们老了
list的removeIf方法

List list1 = Arrays.asList("one","two","three","four","five","six","seven"); List list2 = new ArrayList<>(list1); //删除 boolean result = list2.removeIf(s -> s.length() > 4); System.out.println(result); System.out.println(list2.stream().collect(Collectors.joining(","))); //输出 true one,two,four,five,six //替换 list2.replaceAll(s->s.toUpperCase()); System.out.println(list2.stream().collect(Collectors.joining(","))); //输出 ONE,TWO,FOUR,FIVE,SIX //排序 list2.sort(Comparator.naturalOrder()); System.out.println(list2.stream().collect(Collectors.joining(","))); //输出 FIVE,FOUR,ONE,SIX,TWO

比较

Comparator【JAVA8新方法（也不新啦，我们老啦）】 comparator = Comparator.comparing(Person::getName).thenComparing(Person::getAge); //反向比较 Comparator comparatorReversed = comparator.reversed(); //默认字母顺序 Comparator comparator1 = Comparator.naturalOrder(); //先按空后再按照字母顺序 Comparator comparator2 = Comparator.nullsFirst(Comparator.naturalOrder()); //先按照字母顺序，最后排空 Comparator comparator3 = Comparator.nullsLast(Comparator.naturalOrder()); //比较 Long max = Long.max(1L,2L); BinaryOperator sum = (s1,s2) -> s1 + s2; sum = Long::sum;

hashCode

Long l = 2234324234234324L; int hash = l.hashCode(); System.out.println(hash); hash = Long.hashCode(l); System.out.println(hash); //输出 642554319 642554319

Map forEach，getOrDefault,putIfAbsent

Map map =new HashMap<>(); map.put("key","value"); map.forEach((key,value)-> System.out.println(key+" "+value)); //输出 key value //getOrDefault Person deafulPerson = new Person(); deafulPerson.setName("Test"); Person p = (Person) map.getOrDefault("p",deafulPerson); System.out.println(p.getName()); //输出 TestPerson p1 = new Person(); p1.setName("Test11"); //putIfAbsent map.putIfAbsent("p", p); System.out.println("putIfAbsent=="+map.get("p")); //替换key为p的值为p1 map.replace("p", p1); System.out.println("replace=="+map.get("p")); //替换key值为p的为defaultPeron map.replace("p", p1,deafulPerson); System.out.println("replaceNew=="+map.get("p")); //lambda替换 map.replaceAll((key,oldPerson) -> p1); System.out.println("replaceAll=="+map.get("p")); //输出 putIfAbsent==Person{name='Test', age=0} replace==Person{name='Test11', age=0} replaceNew==Person{name='Test', age=0} replaceAll==Person{name='Test11', age=0}