Java中forEach使用lambda表达式,数组和集合的区别说明

PartnerType[] values = PartnerType.values();
//提示Cannot resolve method 'forEach(<method reference>)
values.forEach(System.out::println);//错误使用

PartnerType[] values = PartnerType.values();
Arrays.stream(values).forEach(System.out::println);//转成流
Arrays.asList(values).forEach(System.out::println);//转成list

ArrayList<String> arrayList = new ArrayList<>();
arrayList.add("a");
arrayList.add("b");
arrayList.add("c");
arrayList.forEach(System.out::println);

HashMap<String, Integer> hashMap = new HashMap<>();
hashMap.put("a",1);
hashMap.put("b",2);
hashMap.put("c",3);
hashMap.put("d",4);
hashMap.forEach((k,v)->System.out.println(k+"_"+v.intValue()));

Map<String, Integer> items = new HashMap<>();
items.put("A", 10);
items.put("B", 20);
items.put("C", 30);
items.put("D", 40);
items.put("E", 50);
items.put("F", 60); 
 
for (Map.Entry<String, Integer> entry : items.entrySet()) {
    System.out.println("Item : " + entry.getKey() + " Count : " + entry.getValue());
}

Map<String, Integer> items = new HashMap<>();
items.put("A", 10);
items.put("B", 20);
items.put("C", 30);
items.put("D", 40);
items.put("E", 50);
items.put("F", 60); 
 
items.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");
    }
});

List<String> items = new ArrayList<>();
items.add("A");
items.add("B");
items.add("C");
items.add("D");
items.add("E"); 
 
for(String item : items){
    System.out.println(item);
}

List<String> items = new ArrayList<>();
items.add("A");
items.add("B");
items.add("C");
items.add("D");
items.add("E"); 
 
//lambda
//Output : A,B,C,D,E
items.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);