As you know, dropWhile for streams was introduced in java 9. But if the target of the project is java 8, you can't use it.
Example code:
public static String getParameterValueOrDefault(String[] args, String paramName, String defaultVal) {
return Arrays.stream(args).sequential().dropWhile(arg->!arg.equals("/"+paramName) && !arg.equals("-"+paramName)).skip(1).findFirst().orElseGet(()->defaultVal);
}
What I want is an equivalent lambda expression written in java 8.
You can use
public static String getParameterValueOrDefault(
String[] args, String paramName, String defaultVal) {
int ix = IntStream.range(0, args.length)
.filter(i -> args[i].matches("[/-]" + Pattern.quote(paramName)))
.map(i -> i + 1)
.findFirst().orElse(args.length);
return ix < args.length? args[ix]: defaultVal;
}
The matches approach is for convenience, if you prefer compact code. If you want an efficient check, you may instead use:
public static String getParameterValueOrDefault(
String[] args, String paramName, String defaultVal) {
int ix = IntStream.range(0, args.length)
.filter(i -> {
String arg = args[i];
return arg.length() == paramName.length() + 1 && arg.endsWith(paramName)
&& (arg.charAt(0) == '-' || arg.charAt(0) == '/');
})
.map(i -> i + 1)
.findFirst().orElse(args.length);
return ix < args.length? args[ix]: defaultVal;
}
I found this way:
public static String getParameterValueOrDefault(String[] args, String paramName, String defaultVal) {
MutableBoolean foundParam = new MutableBoolean(false);
return Arrays.stream(args).sequential().peek(arg->foundParam.value = foundParam.value || arg.equals("/"+paramName) || arg.equals("-"+paramName)).filter(arg->foundParam.value).skip(1).findFirst().orElseGet(()->defaultVal);
}
Where MutableBoolean is:
private static class MutableBoolean {
boolean value;
public MutableBoolean(boolean value) {
this.value = value;
}
}
Related
In ASP NET 6+ I need to make [FromQuery] replace underscores _ and minuses - before matching names.
So I want to plumb ASP to allow [FromQuery] bool testValue to be equivalent to all at once:
[FromQuery(Name="testValue")] bool testValue
[FromQuery(Name="test-value")] bool testValue
[FromQuery(Name="test_value")] bool testValue
Is there a place in the pipeline I can get in before names are compared (to remove _ and - myself)?
My current solution is just to replace the Request.Query with my own doctored QueryCollection that duplicates variables with fixed names in a middleware.
But I'm looking for any answer that's more... unhacky?!
public class RequeryMiddleware : IMiddleware
{
private static readonly char[] separators = new[] { '_', '-', '.', '|' };
private static bool Requery(ref string name)
{
bool changed = false;
if (name.IndexOfAny(separators) >= 0)
{
name = string.Concat(name.Split(separators, StringSplitOptions.None));
changed = true;
}
return changed;
}
public Task InvokeAsync(HttpContext context, RequestDelegate next)
{
Dictionary<string, StringValues> mods = new(
StringComparer.OrdinalIgnoreCase
);
foreach (var item in context.Request.Query)
{
string key = item.Key;
if (Requery(ref key))
{
mods.Add(key, item.Value);
}
}
if (mods.Count > 0)
{
Dictionary<string, StringValues> query = new(
context.Request.Query.Count + mods.Count
, StringComparer.OrdinalIgnoreCase
);
foreach (var item in context.Request.Query)
{
query.Add(item.Key, item.Value);
}
foreach (var mod in mods)
{
// if we get here it's bad...
query.TryAdd(mod.Key, mod.Value);
}
// replace the Query collection
context.Request.Query = new QueryCollection(query);
// change the QueryString too
QueryBuilder qb = new(context.Request.Query);
context.Request.QueryString = qb.ToQueryString();
}
return next(context);
}
}
Not working Query :
select lookup(city, state, tax,'addresslookup')
from (select distinct city, state, tax
from open_glory.addylookup) a
Working Query (without distinct):
select lookup(city, state, tax,'addresslookup')
from (select city, state, tax
from open_glory.addylookup) a
Any help would be appreciated.
UDF code:
Not working Query :
select lookup(city, state, tax,'addresslookup')
from (select distinct city, state, tax
from open_glory.addylookup) a
Working Query (without distinct):
select lookup(city, state, tax,'addresslookup')
from (select city, state, tax
from open_glory.addylookup) a
Any help would be appreciated.
UDF code:
public class Lookup extends GenericUDF {
private static String delimiter = "|";
private ConcurrentHashMap < String, HashMap < String, String >> fileMap = new ConcurrentHashMap < String, HashMap < String, String >> ();
protected String loggedInUser;
protected String loggedInApplication;
private transient GenericUDFUtils.StringHelper returnHelper;
private transient StringConverter[] stringConverter;
private static final Logger LOG = LoggerFactory.getLogger(Lookup.class.getName());
#Override
public ObjectInspector initialize(ObjectInspector[] arguments)
throws UDFArgumentException {
if (arguments.length < 2) {
throw new UDFArgumentLengthException(
"lookup takes 2 or more arguments");
}
stringConverter = new StringConverter[arguments.length];
for (int i = 0; i < arguments.length; i++) {
if (arguments[0].getCategory() != Category.PRIMITIVE) {
throw new UDFArgumentException(
"lookup only takes primitive types");
}
stringConverter[i] = new PrimitiveObjectInspectorConverter.StringConverter(
(PrimitiveObjectInspector) arguments[i]);
}
setLoggedInUser();
returnHelper = new GenericUDFUtils.StringHelper(
PrimitiveCategory.STRING);
LOG.info("initialize successful");
return PrimitiveObjectInspectorFactory.writableStringObjectInspector;
}
private void setLoggedInUser() {
if (loggedInUser == null) {
loggedInUser = SessionState.get().getUserName();
if (loggedInUser != null) {
int idx = loggedInUser.indexOf('.');
loggedInApplication = idx > -1 ? loggedInUser.substring(0, idx) : null;
}
}
}
private void initMap(String f) {
LOG.info("initMap involked");
if (loggedInApplication == null)
throw new NullPointerException(
"Unable to retrieve application name from user.");
String filePath = "/basepath/" + loggedInApplication.toLowerCase() + "/" + f +
".txt";
String line = null;
try {
LOG.info("filePath =" + filePath);
FileSystem fs = FileSystem.get(new Configuration());
FSDataInputStream in = fs.open(new Path(filePath));
BufferedReader br = new BufferedReader(new InputStreamReader( in ));
HashMap < String, String > map = new HashMap < String, String > ();
while ((line = br.readLine()) != null) {
// ignore comment lines
if (line.startsWith("#")) {
continue;
}
String[] strs = line.split("\t");
if (strs.length == 2) {
map.put(strs[0].toUpperCase().trim(), strs[1].trim());
} else if (strs.length > 2) {
map.put(getKey(strs), strs[strs.length - 1].trim());
}
}
fileMap.put(f, map);
br.close();
} catch (Exception e) {
LOG.error(e.getMessage(), e);
}
}
public Text getValue(String s, String f) {
initMap(f);
HashMap < String, String > map = fileMap.get(f);
LOG.info("getValue() fileMap =" + fileMap);
String v = map.get(s);
return v == null ? null : new Text(v);
}
#Override
public Object evaluate(DeferredObject[] arguments) throws HiveException {
String val = buildVal(arguments);
String lookupFile = (String) stringConverter[arguments.length - 1].convert(arguments[arguments.length - 1].get());
Text returnVal = getValue(val.toUpperCase(), lookupFile.toLowerCase());
return returnVal == null ? null : returnHelper.setReturnValue(returnVal.toString());
}
#Override
public String getDisplayString(String[] arg0) {
return "lookup()";
}
private String buildVal(DeferredObject[] arguments) throws HiveException {
StringBuilder builder = new StringBuilder();
int cnt = arguments.length - 1;
for (int i = 0; i < cnt; i++) {
builder.append((String) stringConverter[i].convert(arguments[i].get()));
if (i < cnt - 1) {
builder.append(delimiter);
}
}
return builder.toString();
}
private String getKey(String[] strs) {
StringBuilder builder = new StringBuilder();
int cnt = strs.length - 1;
for (int i = 0; i < cnt; i++) {
builder.append(strs[i].toUpperCase().trim());
if (i < cnt - 1) {
builder.append(delimiter);
}
}
return builder.toString();
}
}
So I have been trying to compare two objects by their fields.
I have noticed there is no equals method in dart. But there are the identical function and the == operator.
I can't seem to understand why there is no equals method. What if I want to do this?
class Name {
String fname;
String lname;
String get firstName => this.fname;
void set firstName(String fname) => this.fname = fname;
String get lastName => this.lname;
void set lastName(String lname) => this.lname = lname;
Name({this.fname, this.lname});
#override
String toString() {
return this.firstName + " " + this.lastName;
}
bool equals(Name n2) {
return this.firstName == n2.firstName && this.lastName == n2.lastName
? true
: false;
}
}
void main(List<String> args) {
Name n1 = new Name();
n1.firstName = "James";
n1.lastName = "Bond";
Name n2 = new Name();
n2.firstName = "James";
n2.lastName = "Bond";
print(n1.equals(n2)); // true
print(identical(n1, n2)); // false
print(n1 == n2); // false
}
What can I do instead of making my own equals. Or does dart expect you to do this manually.
identical will not return true even if the first name and last name of the two objects you are comparing are the same. That's because they are not the same instances. Each instance has its own identity and own hashcode.
You could override the == operator and the hashcode. Then you will be able to compare two different instances. The Equatable-Package already does that for you so you can use the == operator two compare two different instances: https://pub.dev/packages/equatable
You can write code just like this
#override
bool operator ==(Object other) {
if (other.runtimeType != runtimeType)
return false;
/// do smth
}
#override
int get hashCode {
}
My method toString() is supposed to return a string representation of the stack. The string representation consists of the stacks's elements in the order they are stored, enclosed in square brackets. My problem is that I am now returning [element0, element1, element2, element3, element4] so I wonder if there is there a simple way to return the string in reverse order i.e. to return [element4, element3, element2, element1, element0] instead?
public class Stack<E> implements IStack<E> {
public String toString() {
String str = "[";
if (head != null) {
str += head.getmElement();
Node<E> tempNode = head.getmNextNode();
while (tempNode != null) {
str += ", " + tempNode.getmElement();
tempNode = tempNode.getmNextNode();
}
}
str += "]";
return str; }
Node class:
public class Node<E> {
private E mElement;
private Node<E> mNextNode;
Node(E data) {
this.setmElement(data);
}
public E getmElement() {
return this.mElement;
}
public void setmElement(E element) {
this.mElement = element;
}
public Node<E> getmNextNode()
{
return this.mNextNode;
}
public void setmNextNode(Node<E> node)
{
this.mNextNode = node;
}}
You could use a StringBuilder and insert every element at the beginning instead of appending it:
public String toString() {
StringBuilder sb = new StringBuilder("[");
if (head != null) {
sb.append(head.getmElement());
Node<E> tempNode = head.getmNextNode();
while (tempNode != null) {
sb.insert(1, ", ").inser(1, tempNode.getmElement());
tempNode = tempNode.getmNextNode();
}
}
sb.append("]");
return sb.toString();
}
Your list is only forward linked, so you could use a temporary ArrayList and add each element at the index 0.
I am trying to serialize Guava Range objects to JSON using Gson, however the default serialization fails, and I'm unsure how to correctly implement a TypeAdapter for this generic type.
Gson gson = new Gson();
Range<Integer> range = Range.closed(10, 20);
String json = gson.toJson(range);
System.out.println(json);
Range<Integer> range2 = gson.fromJson(json,
new TypeToken<Range<Integer>>(){}.getType());
System.out.println(range2);
assertEquals(range2, range);
This fails like so:
{"lowerBound":{"endpoint":10},"upperBound":{"endpoint":20}}
PASSED: typeTokenInterface
FAILED: range
java.lang.RuntimeException: Unable to invoke no-args constructor for
com.google.common.collect.Cut<java.lang.Integer>. Register an
InstanceCreator with Gson for this type may fix this problem.
at com.google.gson.internal.ConstructorConstructor$12.construct(
ConstructorConstructor.java:210)
...
Note that the default serialization actually loses information - it fails to report whether the endpoints are open or closed. I would prefer to see it serialized similar to its toString(), e.g. [10‥20] however simply calling toString() won't work with generic Range instances, as the elements of the range may not be primitives (Joda-Time LocalDate instances, for example). For the same reason, implementing a custom TypeAdapter seems difficult, as we don't know how to deserialize the endpoints.
I've implemented most of a TypeAdaptorFactory based on the template provided for Multimap which ought to work, but now I'm stuck on the generics. Here's what I have so far:
public class RangeTypeAdapterFactory implements TypeAdapterFactory {
public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
Type type = typeToken.getType();
if (typeToken.getRawType() != Range.class
|| !(type instanceof ParameterizedType)) {
return null;
}
Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
TypeAdapter<?> elementAdapter = (TypeAdapter<?>)gson.getAdapter(TypeToken.get(elementType));
// Bound mismatch: The generic method newRangeAdapter(TypeAdapter<E>) of type
// GsonUtils.RangeTypeAdapterFactory is not applicable for the arguments
// (TypeAdapter<capture#4-of ?>). The inferred type capture#4-of ? is not a valid
// substitute for the bounded parameter <E extends Comparable<?>>
return (TypeAdapter<T>) newRangeAdapter(elementAdapter);
}
private <E extends Comparable<?>> TypeAdapter<Range<E>> newRangeAdapter(final TypeAdapter<E> elementAdapter) {
return new TypeAdapter<Range<E>>() {
#Override
public void write(JsonWriter out, Range<E> value) throws IOException {
if (value == null) {
out.nullValue();
return;
}
String repr = (value.lowerBoundType() == BoundType.CLOSED ? "[" : "(") +
(value.hasLowerBound() ? elementAdapter.toJson(value.lowerEndpoint()) : "-\u221e") +
'\u2025' +
(value.hasLowerBound() ? elementAdapter.toJson(value.upperEndpoint()) : "+\u221e") +
(value.upperBoundType() == BoundType.CLOSED ? "]" : ")");
out.value(repr);
}
public Range<E> read(JsonReader in) throws IOException {
if (in.peek() == JsonToken.NULL) {
in.nextNull();
return null;
}
String[] endpoints = in.nextString().split("\u2025");
E lower = elementAdapter.fromJson(endpoints[0].substring(1));
E upper = elementAdapter.fromJson(endpoints[1].substring(0,endpoints[1].length()-1));
return Range.range(lower, endpoints[0].charAt(0) == '[' ? BoundType.CLOSED : BoundType.OPEN,
upper, endpoints[1].charAt(endpoints[1].length()-1) == '[' ? BoundType.CLOSED : BoundType.OPEN);
}
};
}
}
However the return (TypeAdapter<T>) newRangeAdapter(elementAdapter); line has a compilation error and I'm now at a loss.
What's the best way to resolve this error? Is there a better way to serialize Range objects that I'm missing? What about if I want to serialize RangeSets?
Rather frustrating that the Google utility library and Google serialization library seem to require so much glue to work together :(
This feels somewhat like reinventing the wheel, but it was a lot quicker to put together and test than the time spent trying to get Gson to behave, so at least presently I'll be using the following Converters to serialize Range and RangeSet*, rather than Gson.
/**
* Converter between Range instances and Strings, essentially a custom serializer.
* Ideally we'd let Gson or Guava do this for us, but presently this is cleaner.
*/
public static <T extends Comparable<? super T>> Converter<Range<T>, String> rangeConverter(final Converter<T, String> elementConverter) {
final String NEG_INFINITY = "-\u221e";
final String POS_INFINITY = "+\u221e";
final String DOTDOT = "\u2025";
return new Converter<Range<T>, String>() {
#Override
protected String doForward(Range<T> range) {
return (range.hasLowerBound() && range.lowerBoundType() == BoundType.CLOSED ? "[" : "(") +
(range.hasLowerBound() ? elementConverter.convert(range.lowerEndpoint()) : NEG_INFINITY) +
DOTDOT +
(range.hasUpperBound() ? elementConverter.convert(range.upperEndpoint()) : POS_INFINITY) +
(range.hasUpperBound() && range.upperBoundType() == BoundType.CLOSED ? "]" : ")");
}
#Override
protected Range<T> doBackward(String range) {
String[] endpoints = range.split(DOTDOT);
Range<T> ret = Range.all();
if(!endpoints[0].substring(1).equals(NEG_INFINITY)) {
T lower = elementConverter.reverse().convert(endpoints[0].substring(1));
ret = ret.intersection(Range.downTo(lower, endpoints[0].charAt(0) == '[' ? BoundType.CLOSED : BoundType.OPEN));
}
if(!endpoints[1].substring(0,endpoints[1].length()-1).equals(POS_INFINITY)) {
T upper = elementConverter.reverse().convert(endpoints[1].substring(0,endpoints[1].length()-1));
ret = ret.intersection(Range.upTo(upper, endpoints[1].charAt(endpoints[1].length()-1) == ']' ? BoundType.CLOSED : BoundType.OPEN));
}
return ret;
}
};
}
/**
* Converter between RangeSet instances and Strings, essentially a custom serializer.
* Ideally we'd let Gson or Guava do this for us, but presently this is cleaner.
*/
public static <T extends Comparable<? super T>> Converter<RangeSet<T>, String> rangeSetConverter(final Converter<T, String> elementConverter) {
return new Converter<RangeSet<T>, String>() {
private final Converter<Range<T>, String> rangeConverter = rangeConverter(elementConverter);
#Override
protected String doForward(RangeSet<T> rs) {
ArrayList<String> ls = new ArrayList<>();
for(Range<T> range : rs.asRanges()) {
ls.add(rangeConverter.convert(range));
}
return Joiner.on(", ").join(ls);
}
#Override
protected RangeSet<T> doBackward(String rs) {
Iterable<String> parts = Splitter.on(",").trimResults().split(rs);
ImmutableRangeSet.Builder<T> build = ImmutableRangeSet.builder();
for(String range : parts) {
build.add(rangeConverter.reverse().convert(range));
}
return build.build();
}
};
}
*For inter-process communication, Java serialization would likely work just fine, as both classes implement Serializable. However I'm serializing to disk for more permanent storage, meaning I need a format I can trust won't change over time. Guava's serialization doesn't provide that guarantee.
Here is a Gson JsonSerializer and JsonDeserializer that generically supports a Range: https://github.com/jamespedwards42/Fava/wiki/Range-Marshaller
#Override
public JsonElement serialize(final Range src, final Type typeOfSrc, final JsonSerializationContext context) {
final JsonObject jsonObject = new JsonObject();
if ( src.hasLowerBound() ) {
jsonObject.add( "lowerBoundType", context.serialize( src.lowerBoundType() ) );
jsonObject.add( "lowerBound", context.serialize( src.lowerEndpoint() ) );
} else
jsonObject.add( "lowerBoundType", context.serialize( BoundType.OPEN ) );
if ( src.hasUpperBound() ) {
jsonObject.add( "upperBoundType", context.serialize( src.upperBoundType() ) );
jsonObject.add( "upperBound", context.serialize( src.upperEndpoint() ) );
} else
jsonObject.add( "upperBoundType", context.serialize( BoundType.OPEN ) );
return jsonObject;
}
#Override
public Range<? extends Comparable<?>> deserialize(final JsonElement json, final Type typeOfT, final JsonDeserializationContext context) throws JsonParseException {
if ( !( typeOfT instanceof ParameterizedType ) )
throw new IllegalStateException( "typeOfT must be a parameterized Range." );
final JsonObject jsonObject = json.getAsJsonObject();
final JsonElement lowerBoundTypeJsonElement = jsonObject.get( "lowerBoundType" );
final JsonElement upperBoundTypeJsonElement = jsonObject.get( "upperBoundType" );
if ( lowerBoundTypeJsonElement == null || upperBoundTypeJsonElement == null )
throw new IllegalStateException( "Range " + json
+ "was not serialized with this serializer! The default serialization does not store the boundary types, therfore we can not deserialize." );
final Type type = ( ( ParameterizedType ) typeOfT ).getActualTypeArguments()[0];
final BoundType lowerBoundType = context.deserialize( lowerBoundTypeJsonElement, BoundType.class );
final JsonElement lowerBoundJsonElement = jsonObject.get( "lowerBound" );
final Comparable<?> lowerBound = lowerBoundJsonElement == null ? null : context.deserialize( lowerBoundJsonElement, type );
final BoundType upperBoundType = context.deserialize( upperBoundTypeJsonElement, BoundType.class );
final JsonElement upperBoundJsonElement = jsonObject.get( "upperBound" );
final Comparable<?> upperBound = upperBoundJsonElement == null ? null : context.deserialize( upperBoundJsonElement, type );
if ( lowerBound == null && upperBound != null )
return Range.upTo( upperBound, upperBoundType );
else if ( lowerBound != null && upperBound == null )
return Range.downTo( lowerBound, lowerBoundType );
else if ( lowerBound == null && upperBound == null )
return Range.all();
return Range.range( lowerBound, lowerBoundType, upperBound, upperBoundType );
}
Here is a straight forward solution. Works very well
import com.google.common.collect.BoundType;
import com.google.common.collect.Range;
import com.google.gson.*;
import java.lang.reflect.Type;
public class GoogleRangeAdapter implements JsonSerializer, JsonDeserializer {
public static String TK_hasLowerBound = "hasLowerBound";
public static String TK_hasUpperBound = "hasUpperBound";
public static String TK_lowerBoundType = "lowerBoundType";
public static String TK_upperBoundType = "upperBoundType";
public static String TK_lowerBound = "lowerBound";
public static String TK_upperBound = "upperBound";
#Override
public Object deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
JsonObject jsonObject = (JsonObject)json;
boolean hasLowerBound = jsonObject.get(TK_hasLowerBound).getAsBoolean();
boolean hasUpperBound = jsonObject.get(TK_hasUpperBound).getAsBoolean();
if (!hasLowerBound && !hasUpperBound) {
return Range.all();
}
else if (!hasLowerBound && hasUpperBound){
double upperBound = jsonObject.get(TK_upperBound).getAsDouble();
BoundType upperBoundType = BoundType.valueOf(jsonObject.get(TK_upperBoundType).getAsString());
if (upperBoundType == BoundType.OPEN)
return Range.lessThan(upperBound);
else
return Range.atMost(upperBound);
}
else if (hasLowerBound && !hasUpperBound){
double lowerBound = jsonObject.get(TK_lowerBound).getAsDouble();
BoundType lowerBoundType = BoundType.valueOf(jsonObject.get(TK_lowerBoundType).getAsString());
if (lowerBoundType == BoundType.OPEN)
return Range.greaterThan(lowerBound);
else
return Range.atLeast(lowerBound);
}
else {
double lowerBound = jsonObject.get(TK_lowerBound).getAsDouble();
double upperBound = jsonObject.get(TK_upperBound).getAsDouble();
BoundType upperBoundType = BoundType.valueOf(jsonObject.get(TK_upperBoundType).getAsString());
BoundType lowerBoundType = BoundType.valueOf(jsonObject.get(TK_lowerBoundType).getAsString());
if (lowerBoundType == BoundType.OPEN && upperBoundType == BoundType.OPEN)
return Range.open(lowerBound, upperBound);
else if (lowerBoundType == BoundType.OPEN && upperBoundType == BoundType.CLOSED)
return Range.openClosed(lowerBound, upperBound);
else if (lowerBoundType == BoundType.CLOSED && upperBoundType == BoundType.OPEN)
return Range.closedOpen(lowerBound, upperBound);
else
return Range.closed(lowerBound, upperBound);
}
}
#Override
public JsonElement serialize(Object src, Type typeOfSrc, JsonSerializationContext context) {
JsonObject jsonObject = new JsonObject();
Range<Double> range = (Range<Double>)src;
boolean hasLowerBound = range.hasLowerBound();
boolean hasUpperBound = range.hasUpperBound();
jsonObject.addProperty(TK_hasLowerBound, hasLowerBound);
jsonObject.addProperty(TK_hasUpperBound, hasUpperBound);
if (hasLowerBound) {
jsonObject.addProperty(TK_lowerBound, range.lowerEndpoint());
jsonObject.addProperty(TK_lowerBoundType, range.lowerBoundType().name());
}
if (hasUpperBound) {
jsonObject.addProperty(TK_upperBound, range.upperEndpoint());
jsonObject.addProperty(TK_upperBoundType, range.upperBoundType().name());
}
return jsonObject;
}
}