strem api 最常用:
1.集合的遍历:
java7
List<String> items = new ArrayList<>(); items.add("A"); items.add("B"); items.add("C");for(String item : items){ System.out.println(item); }
java8:
List<String> items = new ArrayList<>(); items.add("A"); items.add("B"); items.add("C");//lambda //Output : A,B,C,D,E items.parallelStream().forEach(item->System.out.println(item)); //Output : C items.forEach(item->{ if("C".equals(item)){ System.out.println(item); } }); //method reference //Output : A,B,C,D,E items.forEach(System.out::println); //Stream and filter //Output : B items.stream() .filter(s->s.contains("B")) .forEach(System.out::println);
java7
Map<String, Integer> items = new HashMap<>(); items.put("A", 10); items.put("B", 20); items.put("C", 30); for (Map.Entry<String, Integer> entry : items.entrySet()) { System.out.println("Item : " + entry.getKey() + " Count : " + entry.getValue()); }
java8:
Map<String, Integer> items = new HashMap<>(); items.put("A", 10); items.put("B", 20); items.put("C", 30); items.parallelStream().forEach((k,v)->System.out.println("Item : " + k + " Count : " + v)); items.forEach((k,v)->{ System.out.println("Item : " + k + " Count : " + v); if("E".equals(k)){ System.out.println("Hello E"); } });
2.数据的过滤 请参考:java8 stream API ListUtils 对 list 数据 分组 ,统计,求和 。。。--https://www.cnblogs.com/lshan/p/10861629.html
原文:https://www.cnblogs.com/lshan/p/10951373.html