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1. Top results related to 8 functions of dictionary in java code list

   • List of objects to map in java 8

     Top Answer

     Answered Feb 12, 2018 · 20 votes

     yourTypes.stream() .collect(Collectors.groupingBy( ObjectA::getType, Collectors.mapping( ObjectA::getId, Collectors.toList())))

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     1/5

   • Java 8 Stream filtering value of list in a list

     Top Answer

     Answered Jan 07, 2015 · 20 votes

     You can do:

     myObjects.stream() .filter(t -> t.getType().equals(someotherType) && t.getSubTypes().stream().anyMatch(<predicate>)) .collect(Collectors.toList());-

     This will fetch all the MyObject objects which

     • meet a criteria regarding the type member.
     • contain objects in the nested List<String> that meet some other criteria, represented with <predicate>

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     2/5

   • Dictionary of ArrayLists in Java

     Top Answer

     Answered Jun 05, 2012 · 2 votes

     Instead of ArrayList grades; you'd have to use ArrayList grades = new ArrayList();

     Yet better: ArrayList<Float> grades = new ArrayList<Float>(); //or use Double or Number

     Note that unlike C or C++ creating a variable doesn't create the object as well. In C++ you could imagine your code as ArrayList* grades; i.e. you'd just create the reference/pointer here.

     Additional thoughts:

     • Dictionary studentGrades; this will be initialized to null.
     • public void main(String[] args) that's not a valid main function since it would have to be static
     • if you have a public static void main(String[] args) you can't use this since you don't have an object instance in the static context
     • You can't instantiate Dictionary since it is abstract. Use one of its subclasses, e.g. new Hashtable<String, List<Float>>(), or a map, e.g. Map<String, List<Float> dictionary = new HashMap<String, List<Float>>();
     • Note that local primitive variables are also not initialized, so this could give you an error too: boolean res; In Java only class members are initialized, local variables are not.

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     3/5

   • List all index of all characters in a string in Java 8

     Top Answer

     Answered Dec 17, 2021 · 2 votes

     A neat trick you can use is to stream the indices of the string, and then collect them by the character at that index:

     Map<Character, List<Integer>> indices = IntStream.range(0, input.length()) .boxed() .collect(Collectors.groupingBy(input::charAt));

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     4/5

   • Java 8 - How to sum all List element in a Map of Lists

     Top Answer

     Answered Feb 03, 2015 · 9 votes

     You have to be aware that you can combine Collectors. See Collectors.groupingBy(Function,Collector)

     Map<Integer, Integer> byId=risks.stream.collect( Collectors.groupingBy(Risk::getId, Collectors.summingInt(Risk::getRiskValue)));-

     You can also combine it with the first operation:

     Map<Integer, Integer> byId=results.stream().map(Risk::new).collect( Collectors.groupingBy(Risk::getId, Collectors.summingInt(Risk::getRiskValue)));

     Note that I assume that you have a method getRiskValue() in your class Risk, otherwise you have to replace Risk::getRiskValue with a lambda expression r -> r.riskValue to access the field, however, having getter methods is always recommended.

     The result maps from id to total.

     After reading your question again, I noticed that you actually want to sum up riskValue and store it within totRisk of each (?) Risk instance. This is a bit more complicated as it doesn’t fit the common usage pattern:

     Map<Integer, List<Risk>> byId=results.stream().map(Risk::new).collect( Collectors.groupingBy(Risk::getId, Collectors.collectingAndThen( Collectors.toList(), l-> { int total=l.stream().collect(Collectors.summingInt(r -> r.riskValue)); l.forEach(r->r.totRisk=total); return l; })));

     at this point we really should switch to using import static java.util.stream.Collectors.*;:

     Map<Integer, List<Risk>> byId=results.stream().map(Risk::new).collect( groupingBy(Risk::getId, collectingAndThen(toList(), l-> { int total=l.stream().collect(summingInt(r -> r.riskValue)); l.forEach(r->r.totRisk=total); return l; })));

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     5/5

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2. www.geeksforgeeks.org › java-util-dictionary-classJava.util.Dictionary Class in Java - GeeksforGeeks

   www.geeksforgeeks.org › java-util-dictionary-class

   • Cached

   Apr 9, 2023 · The java.util.Dictionary class is a class in Java that provides a key-value data structure, similar to the Map interface. It was part of the original Java Collections framework and was introduced in Java 1.0. However, the Dictionary class has since been considered obsolete and its use is generally discouraged.

3. www.geeksforgeeks.org › dictionary-elements-methodDictionary elements() Method in Java with Examples

   www.geeksforgeeks.org › dictionary-elements-method

   • Cached

   Dec 27, 2018 · The keys () method of Dictionary class in Java is used to get the enumeration of the values present in the dictionary. Syntax: Enumeration enu = DICTIONARY.elements() Parameters: The method does not take any parameters. Return value: The method returns an enumeration of the values of the Dictionary. Below programs are used to illustrate the ...

4. People also ask

   What is a dictionary in Java?

   • Dictionary () Sole constructor. The java.util.Dictionary class is a class in Java that provides a key-value data structure, similar to the Map interface. It was part of the original Java Collections framework and was introduced in Java 1.0. However, the Dictionary class has since been considered obsolete and its use is generally discouraged.

   Java.util.Dictionary Class in Java - GeeksforGeeks

   www.geeksforgeeks.org/java-util-dictionary-class-java/

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   How to get enumeration of a dictionary in Java?

   • The keys () method of Dictionary class in Java is used to get the enumeration of the values present in the dictionary. Syntax: Parameters: The method does not take any parameters. Return value: The method returns an enumeration of the values of the Dictionary. Program 2: A Computer Science portal for geeks.

   Dictionary elements() Method in Java with Examples

   www.geeksforgeeks.org/dictionary-elements-method-in-java-with-examples/

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   Why should you learn Java dictionaries?

   • Understanding Java dictionaries is also a stepping stone to mastering more complex data structures and algorithms. For example, the concept of hashing, which is fundamental to dictionaries, is also used in hash tables, bloom filters, and hash functions.

   Java Dictionary | Hashmaps and Hashtables Guide

   ioflood.com/blog/java-dictionary/

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   Can a Java dictionary have null keys & values?

   • One common issue that you may encounter when working with Java dictionaries is dealing with null keys and values. While HashMap allows one null key and any number of null values, Hashtable doesn’t allow any null keys or values. Trying to put a null key or value in a Hashtable will result in a NullPointerException. Here’s an example:

   Java Dictionary | Hashmaps and Hashtables Guide

   ioflood.com/blog/java-dictionary/

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5. docs.oracle.com › javase › 8Uses of Class java.util.Dictionary (Java Platform SE 8 ) - Oracle

   docs.oracle.com › javase › 8

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   Description. java.security. Provides the classes and interfaces for the security framework. java.util. Contains the collections framework, legacy collection classes, event model, date and time facilities, internationalization, and miscellaneous utility classes (a string tokenizer, a random-number generator, and a bit array). javax.swing.

6. ioflood.com › blog › java-dictionaryJava Dictionary | Hashmaps and Hashtables Guide

   ioflood.com › blog › java-dictionary

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   Nov 9, 2023 · Creating a Java Dictionary. Creating a Java dictionary is a straightforward process. You can use either the HashMap or Hashtable class, both of which are part of Java’s standard library. Here’s how you can create a dictionary using the HashMap class: HashMap<String, Integer> myDictionary = new HashMap<>(); In this code block, we’ve ...

7. www.tutorialspoint.com › dictionary-methods-in-javaDictionary Methods in Java - Online Tutorials Library

   www.tutorialspoint.com › dictionary-methods-in-java

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   Sep 24, 2019 · 3. boolean isEmpty ( ) Returns true if the dictionary is empty, and returns false if it contains at least one key. 4. Enumeration keys ( ) Returns an enumeration of the keys contained in the dictionary. 5. Object put (Object key, Object value) Inserts a key and its value into the dictionary.

   Code sample

   Dictionary dictionary = new Hashtable();

   dictionary.put("20", "John");

   dictionary.put("40", "Tom");

   dictionary.put("60", "Steve");

   dictionary.put("80", "Kevin");...

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8. stackoverflow.com › questions › 1145175What's the most practical way to have "functions in a ...

   stackoverflow.com › questions › 1145175

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   Jul 19, 2013 · When programming with C/C++ or Python I sometimes used to have a dictionary with references to functions according to the specified keys. However, I don't really know how to have the same -- or at the very least similar -- behavior in Java allowing me dynamic key-function (or method, in Java slang) association.

9. docs.oracle.com › en › javaUses of Class java.util.Dictionary (Java SE 11 & JDK 11 )

   docs.oracle.com › en › java

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   Uses of Classjava.util.Dictionary. Uses of Class. java.util.Dictionary. Provides the classes and interfaces for the security framework. Contains the collections framework, some internationalization support classes, a service loader, properties, random number generation, string parsing and scanning classes, base64 encoding and decoding, a bit ...