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

   • List of objects to map in java 8

     Top Answer

     Answered Feb 12, 2018 · 21 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 Dictionary class defines the following methods: get (Object key): Returns the value associated with the specified key in the dictionary, or null if the key is not found. put (Object key, Object value): Inserts a key-value pair into the dictionary. If the key already exists, its corresponding value is.

3. docs.oracle.com › api › javaDictionary (Java Platform SE 8 ) - Oracle

   docs.oracle.com › api › java

   • Cached

   The Dictionary class is the abstract parent of any class, such as Hashtable, which maps keys to values. Every key and every value is an object. In any one Dictionary object, every key is associated with at most one value. Given a Dictionary and a key, the associated element can be looked up. Any non- null object can be used as a key and as a value.

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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   What is a dictionary class?

   • The Dictionary class is the abstract parent of any class, such as Hashtable, which maps keys to values. Every key and every value is an object. In any one Dictionary object, every key is associated with at most one value. Given a Dictionary and a key, the associated element can be looked up.

   Dictionary (Java Platform SE 8 ) - docs.oracle.com

   docs.oracle.com/javase/8/docs//api/java/util/Dictionary.html

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   How do dictionaries work in Java?

   • To truly grasp the working of Java dictionaries, it’s essential to understand the concept of hashing. Hashing is a process that takes an input (or ‘message’) and returns a fixed-size string of bytes, typically in the form of a ‘hash code’.

   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. 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.

   Code sample

   private static Map<String, Action<Foo>> getActions() {

     Action<Foo> firstAction = new Action<Foo>() {

     @Override public void execute(Foo item) {

     }

     };...

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

   www.geeksforgeeks.org › dictionary-elements-method

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   Dec 27, 2018 · Dictionary<Integer, String> dict. = new Hashtable<Integer, String>(); dict.put(10, "Geeks"); dict.put(15, "4"); dict.put(20, "Geeks"); dict.put(25, "Welcomes"); dict.put(30, "You"); System.out.println("The Dictionary is: " + dict); Enumeration enu = dict.elements();

7. 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.

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

   ioflood.com › blog › java-dictionary

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   Nov 9, 2023 · In Java, dictionaries are created using HashMap or Hashtable classes, with the syntax HashMap<String, Integer> map = new HashMap<>();. These classes allow you to store and retrieve data in the form of key-value pairs, similar to a real-world dictionary. Here’s a simple example of creating a HashMap: HashMap<String, Integer> map = new HashMap<>();

10. 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 · Following is an example implementing put() and get() method of the Dictionary class −. Example import java.util.*; public class Demo { public static void main(String[] args) { Dictionary dictionary = new Hashtable(); dictionary.put("20", "John"); dictionary.put("40", "Tom"); dictionary.put("60", "Steve"); dictionary.put("80", "Kevin ...