Would someone help me with getting the array of the map values with stream and filtering?
public class TheMap extends HashMap<String, String> {
public TheMap(String name, String title) {
super.put("name", name);
super.put("title", title);
}
public static void main(final String[] args) {
Map<Long, Map<String, String>>map = new HashMap<>();
map.put(0L, null);
map.put(1L, new TheMap("jane", "engineer"));
map.put(2L, new TheMap("john", "engineer"));
map.put(3L, new TheMap(null, "manager"));
map.put(4L, new TheMap("who", null));
map.put(5L, new TheMap(null, null));
}
}
The result that I am looking for is an ArrayList<TheMap> with only these two entries:
TheMap("jane", "engineer")
TheMap("john", "engineer")
Basically, retrieve TheMap with none-null name and title.
List<Map<String, String>> list =
map.values().stream().filter(v ->
v != null &&
!v.entrySet().isEmpty() &&
!v.containsValue(null)).
collect(Collectors.toList());
If you need an arrayList of TheMap, try the following way:
ArrayList<TheMap> as = map.values()
.stream()
.filter(v -> v != null && v.get("name") != null && v.get("title") != null)
.map(m -> (TheMap)m)
.collect(Collectors.toCollection(ArrayList::new)));
Related
I want to read mulitpart/formdata, one part is application/JSON. I can't get them to Map<String,String>, Is there any way to parse Part to String?
private Map<String, String> getFormData(String path, MultiValueMap<String, Part> partMultiValueMap) {
if (partMultiValueMap != null) {
Map<String, String> formData = new HashMap<>();
Map<String, Part> multiPartMap = partMultiValueMap.toSingleValueMap();
for (Map.Entry<String, Part> partEntry : multiPartMap.entrySet()) {
Part part = partEntry.getValue();
if (part instanceof FormFieldPart) {
formData.put(partEntry.getKey(), ((FormFieldPart) part).value());
} else {
String bodyString = bufferToStr(part.content());
formData.put(partEntry.getKey(), bodyString);
}
}
return formData;
}
return null;
}
extra Flux
private String bufferToStr(Flux<DataBuffer> content){
AtomicReference<String> res = new AtomicReference<>();
content.subscribe(buffer -> {
byte[] bytes = new byte[buffer.readableByteCount()];
buffer.read(bytes);
DataBufferUtils.release(buffer);
res.set(new String(bytes, StandardCharsets.UTF_8));
});
return res.get();
}
Subscribe is async; bufferToStr value may be null?
You could do it in non-blocking way with StringDecoder
Basically you could write your code to return Mono<Map<>>
Note: I'm using Pair class here to return key-value and later collect them to Map
Pair I'm using here is from package org.springframework.data.util.Pair
public Mono<Map<String, String>> getFormData(MultiValueMap<String, Part> partMultiValueMap) {
Map<String, Part> multiPartMap = partMultiValueMap.toSingleValueMap();
return Flux.fromIterable(multiPartMap.entrySet())
.flatMap(entry -> {
Part part = entry.getValue();
if (part instanceof FormFieldPart) {
return Mono.just(
Pair.of(entry.getKey(), ((FormFieldPart) part).value()) // return Pair
);
} else {
return decodePartToString(part.content()) // decoding DataBuffers to string
.flatMap(decodedString ->
Mono.just(Pair.of(entry.getKey(), decodedString))); // return Pair
}
})
.collectMap(Pair::getFirst, Pair::getSecond); // map and collect pairs to Map<>
}
private Mono<String> decodePartToString(Flux<DataBuffer> dataBufferFlux) {
StringDecoder stringDecoder = StringDecoder.textPlainOnly();
return stringDecoder.decodeToMono(dataBufferFlux,
ResolvableType.NONE,
MimeTypeUtils.TEXT_PLAIN,
Collections.emptyMap()
);
}
I was going through How to remove a key from HashMap while iterating over it?, but my requirement is bit different.
class Main {
public static void main(String[] args) {
Map<String, String> hashMap = new HashMap<>();
hashMap.put("RED", "#FF0000");
hashMap.put("BLACK", null);
hashMap.put("BLUE", "#0000FF");
hashMap.put("GREEN", "#008000");
hashMap.put("WHITE", null);
// I wan't result like below - get All keys whose value is null
List<String> collect = hashMap.values()
.stream()
.filter(e -> e == null)
.collect(Collectors.toList());
System.out.println(collect);
// Result - BLACK, WHITE in list
}
}
Try this:
import java.util.*;
import java.util.stream.*;
class Main {
public static void main(String[] args) {
Map<String, String> hashMap = new HashMap<>();
hashMap.put("RED", "#FF0000");
hashMap.put("BLACK", null);
hashMap.put("BLUE", "#0000FF");
hashMap.put("GREEN", "#008000");
hashMap.put("WHITE", null);
// I wan't result like below - get All keys whose value is null
List<String> collect = hashMap.keySet()
.stream()
.filter(e -> Objects.isNull(hashMap.get(e)))
.collect(Collectors.toList());
System.out.println(collect);
// Result - BLACK, WHITE in list
}
}
As pointed out in the comments, you can try this as well:
import java.util.*;
import java.util.stream.*;
class Main {
public static void main(String[] args) {
Map<String, String> hashMap = new HashMap<>();
hashMap.put("RED", "#FF0000");
hashMap.put("BLACK", null);
hashMap.put("BLUE", "#0000FF");
hashMap.put("GREEN", "#008000");
hashMap.put("WHITE", null);
// I wan't result like below - get All keys whose value is null
List<String> collect = hashMap.entrySet()
.stream()
.filter(e -> Objects.isNull(e.getValue()))
.map(e -> e.getKey())
.collect(Collectors.toList());
System.out.println(collect);
// Result - BLACK, WHITE in list
}
}
This is more optimized, as compared to the first solution.
How do I achieve this using java=8
I have a CSV in below format and from this i want to populate Map<String, Map<String, String>
where the outer map will have key scriptId and transationType as these are the distinct Type and inner map for scriptId key should contain first 5 values stating from position 2 as key and 3 as value.
<scriptId<
<TATA,TATA Moters>
<REL,Reliance Industries Ltd>
<LNT, L&T>
<SBI, State Bank of India>>
<transactionType,<
<P,B>
<S,S>>
Content of CSV File
Type,ArcesiumValue,GICValue
scriptId,TATA,TATA Moters
scriptId,REL,Reliance Industries Ltd
scriptId,LNT,L&T
scriptId,SBI,State Bank of India
transactionType,P,B
transactionType,S,S
How do i generate this using Java8
public void loadReferenceData() throws IOException {
List<Map<String, Map<String, String>>> cache = Files.lines(Paths.get("data/referenceDataMapping.csv")).skip(1)
.map(mapRefereneData).collect(Collectors.toList());
System.out.println(cache);
}
public static Function<String, Map<String, Map<String, String>>> mapRefereneData = (line) -> {
String[] sp = line.split(",");
Map<String, Map<String, String>> cache = new HashMap<String, Map<String, String>>();
try {
if (cache.containsKey(sp[0])) {
cache.get(sp[0]).put(sp[1], sp[2]);
} else {
Map<String, String> map = new HashMap<String, String>();
map.put(sp[1], sp[2]);
cache.put(sp[0], map);
}
} catch (NumberFormatException e) {
e.printStackTrace();
}
return cache;
};
Well it is much simpler to use two Collectors:
Map<String, Map<String, String>> groupCSV = Files.lines(Paths.get("..."))
.skip(1L).map(l -> l.split(","))
.collect(Collectors.groupingBy(a -> a[0], Collectors.toMap(a -> a[1], a -> a[2])));
I want to serialize an Object to Map by Moshi.Here is my codes by Gson
public static Map<String, String> toMap(Object obj, Gson gson) {
if (gson == null) {
gson = new Gson();
}
String json = gson.toJson(obj);
Map<String, String> map = gson.fromJson(json, new TypeToken<Map<String, String>>() {
}.getType());
return map;
}
And how to write by Moshi ?
Here's one way. Check out the toJsonValue doc here.
Moshi moshi = new Moshi.Builder().build();
JsonAdapter<Object> adapter = moshi.adapter(Object.class);
Object jsonStructure = adapter.toJsonValue(obj);
Map<String, Object> jsonObject = (Map<String, Object>) jsonStructure;
If you know the type of obj, it'd be better to look up the adapter of that type, rather than of Object. (The Object JsonAdadpter has to look up the runtime type on every toJson call.
#NanoJava8 solution crashes but can be made to work with a minor change using Map instead of HashMap
Type type = Types.newParameterizedType(Map.class, String.class, String.class);
JsonAdapter<Map<String,String>> adapter = moshi.adapter(type);
Map<String,String> map = adapter.fromJson(json);
As stated by Jesse in the answer Moshi support fields as Map but not HashMap.
In Kotlin:
val type = Types.newParameterizedType(
MutableMap::class.java,
String::class.java,
String::class.java
)
val adapter: JsonAdapter<Map<String, String>> = moshi.adapter(type)
val map: Map<String, String> = adapter.fromJson(responseJson)
Type type = Types.newParameterizedType(HashMap.class, String.class, String.class);
JsonAdapter<Map<String,String>> adapter = moshi.adapter(type);
Map<String,String> map = adapter.fromJson(json);
class HashMapJsonAdapter<K, V>(
private val keyAdapter: JsonAdapter<K>,
private val valueAdapter: JsonAdapter<V>
) : JsonAdapter<HashMap<K, V>>() {
#Throws(IOException::class)
override fun toJson(writer: JsonWriter, map: HashMap<K, V>?) {
writer.beginObject()
for ((key, value) in map ?: emptyMap<K, V>()) {
if (key == null) {
throw JsonDataException("Map key is null at ${writer.path}")
}
keyAdapter.toJson(writer, key)
valueAdapter.toJson(writer, value)
}
writer.endObject()
}
#Throws(IOException::class)
override fun fromJson(reader: JsonReader): HashMap<K, V>? {
val result = linkedMapOf<K, V>()
reader.beginObject()
while (reader.hasNext()) {
val name = keyAdapter.fromJson(reader)
val value = valueAdapter.fromJson(reader)
val replaced = result.put(name!!, value!!)
if (replaced != null) {
throw JsonDataException("Map key '$name' has multiple values at path ${reader.path} : $replaced and value")
}
}
reader.endObject()
return result
}
override fun toString(): String = "JsonAdapter($keyAdapter=$valueAdapter)"
companion object
}
I am trying to do a nested null check and then clear the values in map in the nested object if the map is not null.
The following is my hypothetical code. I am wondering if this is the right way to do it or is there a more elegant solution to this.
package exp.myJavaLab.Experiments;
import java.util.*;
public class OptionalTest {
public Inner inner;
public static void main(String[] args) {
OptionalTest testObj = new OptionalTest();
Pojo pojo1 = new Pojo();
pojo1.id = 1;
Map<String, String> dataMap = new HashMap<>();
dataMap.put("a","b");
pojo1.dataMap = dataMap;
Pojo pojo2 = new Pojo();
pojo2.id = 2;
Inner inner = new Inner();
inner.pojoList = Arrays.asList(pojo1, pojo2);
testObj.inner = inner;
System.out.println(testObj);
Optional.ofNullable(testObj.inner)
.map(Inner::getPojoList)
.ifPresent(pojos -> pojos.forEach(pojo -> {
if (pojo.getDataMap() != null) {
pojo.getDataMap().clear();
}
}));
System.out.println(testObj);
}
#Override
public String toString() {
final StringBuilder sb = new StringBuilder("OptionalTest{");
sb.append("inner=").append(inner);
sb.append('}');
return sb.toString();
}
}
class Inner {
public List<Pojo> pojoList;
public List<Pojo> getPojoList() {
return pojoList;
}
#Override
public String toString() {
final StringBuilder sb = new StringBuilder("Inner{");
sb.append("pojoList=").append(pojoList);
sb.append('}');
return sb.toString();
}
}
class Pojo {
public Map<String, String> dataMap;
public int id;
#Override
public String toString() {
final StringBuilder sb = new StringBuilder("Pojo{");
sb.append("dataMap=").append(dataMap);
sb.append(", id=").append(id);
sb.append('}');
return sb.toString();
}
public Map<String, String> getDataMap() {
return dataMap;
}
public int getId() {
return id;
}
}
In my opinion Collections should never be null.
You could declare your pojoList and dataMap as private and instantiate them.
Your class then needs some add-methods. So you are sure getDataMap() never returns null:
class Pojo {
private Map<String, String> dataMap = new HashMap<>();
public Map<String, String> getDataMap() {
return dataMap;
}
public void add(String key, String value) {
dataMap.put(key, value);
}
}
Then you don't need to check for null:
Optional.ofNullable(testObj.inner)
.map(Inner::getPojoList)
.ifPresent(pojos -> pojos.forEach(pojo -> { pojo.getDataMap().clear(); }));