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這篇文章主要介紹了Java中List使用stream流轉成map的方法有哪些的相關知識，內容詳細易懂，操作簡單快捷，具有一定借鑒價值，相信大家閱讀完這篇Java中List使用stream流轉成map的方法有哪些文章都會有所收獲，下面我們一起來看看吧。
public class Person {
private String name;
private String address;
public Person(String name, String address) {
this.name = name;
this.address = address;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
} List<Person> list = new ArrayList<>();
Person person1 = new Person("熊大","森林第一個小屋");
Person person2 = new Person("熊二","森林第二個小屋");
Person person3 = new Person("光頭強","森林第三個小屋");
Person person4 = new Person("熊大","森林第四個小屋");
list.add(person1);
list.add(person2);
list.add(person3);
list.add(person4);
Map<String,Person> map = list.stream().collect(Collectors.toMap(Person::getName,each->each,(value1, value2) -> value1));
System.out.println(JSON.toJSONString(map));控制臺打印日志:
{“光頭強”:{“address”:“森林第三個小屋”,“name”:“光頭強”},“熊大”:{“address”:“森林第一個小屋”,“name”:“熊大”},“熊二”:{“address”:“森林第二個小屋”,“name”:“熊二”}}
List<Person> list = new ArrayList<>();
Person person1 = new Person("熊大","森林第一個小屋");
Person person2 = new Person("熊二","森林第二個小屋");
Person person3 = new Person("光頭強","森林第三個小屋");
Person person4 = new Person("熊大","森林第四個小屋");
list.add(person1);
list.add(person2);
list.add(person3);
list.add(person4);
Map<String,String> map = list.stream().collect(Collectors.toMap(Person::getName,Person::getAddress,(value1, value2) -> value1));
System.out.println(JSON.toJSONString(map));控制臺打印日志:
{“光頭強”:“森林第三個小屋”,“熊大”:“森林第一個小屋”,“熊二”:“森林第二個小屋”}
List<Person> list = new ArrayList<>();
Person person1 = new Person("熊大","森林第一個小屋");
Person person2 = new Person("熊二","森林第二個小屋");
Person person3 = new Person("光頭強","森林第三個小屋");
Person person4 = new Person("熊大","森林第四個小屋");
list.add(person1);
list.add(person2);
list.add(person3);
list.add(person4);
Map<String, List<Person>> map = list.stream().collect(Collectors.groupingBy(Person::getName));
System.out.println(JSON.toJSONString(map));控制臺打印日志:
{“光頭強”:[{“address”:“森林第三個小屋”,“name”:“光頭強”}],“熊大”:[{“address”:“森林第一個小屋”,“name”:“熊大”},{“address”:“森林第四個小屋”,“name”:“熊大”}],“熊二”:[{“address”:“森林第二個小屋”,“name”:“熊二”}]}
List<Person> list = new ArrayList<>();
Person person1 = new Person("熊大","森林第一個小屋");
Person person2 = new Person("熊二","森林第二個小屋");
Person person3 = new Person("光頭強","森林第三個小屋");
Person person4 = new Person("熊大","森林第四個小屋");
list.add(person1);
list.add(person2);
list.add(person3);
list.add(person4);
Map<String,List<Person>> map = list.stream().collect(Collectors.toMap(Person::getName,each->Collections.singletonList(each),(value1, value2) -> {
List<Person> union = new ArrayList<>(value1);
union.addAll(value2);
return union;
}));
System.out.println(JSON.toJSONString(map));控制臺打印日志:
{“光頭強”:[{“address”:“森林第三個小屋”,“name”:“光頭強”}],“熊大”:[{“address”:“森林第一個小屋”,“name”:“熊大”},{“address”:“森林第四個小屋”,“name”:“熊大”}],“熊二”:[{“address”:“森林第二個小屋”,“name”:“熊二”}]}
List<Person> list = new ArrayList<>();
Person person1 = new Person("熊大","森林第一個小屋");
Person person2 = new Person("熊二","森林第二個小屋");
Person person3 = new Person("光頭強","森林第三個小屋");
Person person4 = new Person("熊大","森林第四個小屋");
list.add(person1);
list.add(person2);
list.add(person3);
list.add(person4);
Map<String,List<String>> map = list.stream().collect(Collectors.toMap(Person::getName,each->Collections.singletonList(each.getAddress()),(value1, value2) -> {
List<String> union = new ArrayList<>(value1);
union.addAll(value2);
return union;
}));
System.out.println(JSON.toJSONString(map));控制臺打印日志:
{“光頭強”:[“森林第三個小屋”],“熊大”:[“森林第一個小屋”,“森林第四個小屋”],“熊二”:[“森林第二個小屋”]}
List<Map<String,Object>> list = new ArrayList<>();
Person person1 = new Person("熊大","森林第一個小屋");
Person person2 = new Person("熊二","森林第二個小屋");
Person person3 = new Person("光頭強","森林第三個小屋");
Map<String,Object> map1 = new HashMap<>();
map1.put("id","1");
map1.put("person",person1);
Map<String,Object> map2 = new HashMap<>();
map2.put("id","2");
map2.put("person",person2);
Map<String,Object> map3 = new HashMap<>();
map3.put("id","3");
map3.put("person",person3);
list.add(map1);
list.add(map2);
list.add(map3);
Map<String,Map<String,Object>> map = list.stream().collect(Collectors.toMap(each->Objects.toString(each.get("id"),""),each->each,(key1,key2)->key1));
System.out.println(JSON.toJSONString(map));控制臺打印日志:
{“1”:{“person”:{“address”:“森林第一個小屋”,“name”:“熊大”},“id”:“1”},“2”:{“person”:{“address”:“森林第二個小屋”,“name”:“熊二”},“id”:“2”},“3”:{“person”:{“address”:“森林第三個小屋”,“name”:“光頭強”},“id”:“3”}}
List<Map<String,Object>> list = new ArrayList<>();
Person person1 = new Person("熊大","森林第一個小屋");
Person person2 = new Person("熊二","森林第二個小屋");
Person person3 = new Person("光頭強","森林第三個小屋");
Map<String,Object> map1 = new HashMap<>();
map1.put("id","1");
map1.put("person",person1);
Map<String,Object> map2 = new HashMap<>();
map2.put("id","2");
map2.put("person",person2);
Map<String,Object> map3 = new HashMap<>();
map3.put("id","3");
map3.put("person",person3);
list.add(map1);
list.add(map2);
list.add(map3);
Map<String,Object> map = list.stream().collect(Collectors.toMap(each->Objects.toString(each.get("id"),""),each->each.get("person"),(key1,key2)->key1));
System.out.println(JSON.toJSONString(map));控制臺打印日志:
{“1”:{“address”:“森林第一個小屋”,“name”:“熊大”},“2”:{“address”:“森林第二個小屋”,“name”:“熊二”},“3”:{“address”:“森林第三個小屋”,“name”:“光頭強”}}
List<Map<String,String>> list = new ArrayList<>();
Map<String,String> map1 = new HashMap<>();
map1.put("id","1");
map1.put("name","熊大");
map1.put("address","森林第一個小屋");
Map<String,String> map2 = new HashMap<>();
map2.put("id","2");
map2.put("name","熊二");
map2.put("address","森林第二個小屋");
Map<String,String> map3 = new HashMap<>();
map3.put("id","3");
map3.put("name","光頭強");
map3.put("address","森林第三個小屋");
list.add(map1);
list.add(map2);
list.add(map3);
Map<String,Map<String,String>> map = list.stream().collect(Collectors.toMap(each->each.get("id"),each->each,(key1,key2)->key1));
System.out.println(JSON.toJSONString(map));控制臺打印日志:
{“1”:{“address”:“森林第一個小屋”,“name”:“熊大”,“id”:“1”},“2”:{“address”:“森林第二個小屋”,“name”:“熊二”,“id”:“2”},“3”:{“address”:“森林第三個小屋”,“name”:“光頭強”,“id”:“3”}}
List<Map<String,String>> list = new ArrayList<>();
Map<String,String> map1 = new HashMap<>();
map1.put("id","1");
map1.put("name","熊大");
map1.put("address","森林第一個小屋");
Map<String,String> map2 = new HashMap<>();
map2.put("id","2");
map2.put("name","熊二");
map2.put("address","森林第二個小屋");
Map<String,String> map3 = new HashMap<>();
map3.put("id","3");
map3.put("name","光頭強");
map3.put("address","森林第三個小屋");
list.add(map1);
list.add(map2);
list.add(map3);
Map<String,String> map = list.stream().collect(Collectors.toMap(each->each.get("id"),each->each.get("name"),(key1,key2)->key1));
System.out.println(JSON.toJSONString(map));控制臺打印日志:
{“1”:“熊大”,“2”:“熊二”,“3”:“光頭強”}
關于“Java中List使用stream流轉成map的方法有哪些”這篇文章的內容就介紹到這里，感謝各位的閱讀！相信大家對“Java中List使用stream流轉成map的方法有哪些”知識都有一定的了解，大家如果還想學習更多知識，歡迎關注億速云行業資訊頻道。
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