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1. Top results related to what are the uses of a dictionary in java

   • What are the uses of inner classes in Java? Are nested classes and inner classes the same?

     Top Answer

     Answered Jun 20, 2020 · 13 votes

     No, they're not the same: an inner class is non-static.

     JLS 8.1.3 Inner Classes and Enclosing Instances

     An inner class is a nested class that is not explicitly or implicitly declared static.

     Consult also the following diagram from Joe Darcy:

     Joseph D. Darcy's Oracle Weblog - Nested, Inner, Member, and Top-Level Classes

     Related questions

     • Java inner class and static nested class

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   • What are the uses of constructor reference in java 8

     Top Answer

     Answered May 23, 2017 · 7 votes

     First of all, you should understand that constructor references are just a special form of method references. The point about method references is that they do not invoke the referenced method but provide a way to define a function which will invoke the method when being evaluated.

     The linked article’s examples might not look that useful but that’s the general problem of short self-contained example code. It’s just the same as with the “hello world” program. It’s not more useful than typing the text “hello world” directly into the console but it’s not meant to be anyway. It’s purpose is to demonstrate the programming language.

     As assylias has shown, there are use cases involving already existing functional interfaces using the JFC API.

     Regarding the usefulness of a custom functional interface that’ll be used together with a constructor reference, you have to think about the reason to use (functional) interface in general: abstraction.

     Since the purpose of an interface is to abstract the underlying operation, the use cases are the places where you do not want to perform an unconditional new SomeType(…) operation.

     So one example is the commonly known Factory pattern where you define an interface to construct an object and implementing the factory via constructor reference is only one option out of the infinite possibilities.

     Another important point are all kinds of Generic methods where the possibility to construct instances of the type, that is not known due to type erasure, is needed. They can be implemented via a function which is passed as parameter and whether one of the existing functional interfaces fits or a custom one is needed simply depends on the required number and types of parameters.

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   • What are the problems of using `break` statement in a `while` loop in Java?

     Top Answer

     Answered Oct 04, 2016 · 1 votes

     IMO, using break in a while loop isn't that bad. But I can guess why the speaker said that.

     So if I have a while loop like this:

     while (condition1) { if (condition2) { break; } // do other stuff}

     You can definitely make the code shorter by doing this:

     while(condition1 && !condition2) { // do other stuff}

     The speaker might think that breaks in a while loop are not neccessary because you can just write all the conditions where you are supposed to write them i.e. in the parantheses.

     However, this is not the case. If I have this while loop:

     while (condition1) { // do other stuff if (condition2) { break; }}

     How do you change that so it doesn't use break?

     while (condition1) { // do other stuff if (condition2) { condition1 = false; }}

     That doesn't seem really nice to me.

     Let's put this into a piece of kind of meaningful code. Which do you think is more readable:

     while(noWallInFront) { walk(); if (sawFriend) { sayHi(); break; }}

     or

     while(noWallInFront) { walk(); if (sawFriend) { sayHi(); noWallInFront = false; }}

     Obviously the first one, right? The second one sounds like you're treating your firend like a wall.

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     3/5

   • What are the disadvantages of using a static nested class in Java?

     Top Answer

     Answered Nov 06, 2012 · 5 votes

     Advantage: What the author meant was a static nested class gets compiled into a totally separate .class than the outer class enclosing it. So, if it bothers you or over complicates the things or confuses you then better use it separately. A Static nested class doesn't depend on the outer class instance, it can run on it's own. Even a main function can be written inside the static nested class and invoked directly. And the benefit of it is you can have less number of objects created at runtime which wouldn't be the case with other types of nested classes.

     Disadvantage The only disadvantage I can think of is a static nested class has access to both the protected and private members of the outer class. Say you have a class X and a class Y. In order for Y to access X's private members but not the rest of the world, making Y an Inner class of X helps. That satisfies the encapsulation thing by grouping them together.

     But a Static Nested class doesn't care about accessibility modifiers of the Outer class while accessing it's members. Since it can live independently, it can allow somebody from outer world to mingle with the private members of the Outer class and hence break the encapsulation.

     Treat the Static nested class as another top level class who can gain access to the private and protected members of the Outer class without using the Outer class's context/instance and freely sell them to external world for bad use.

     For better understanding about Nested classes or anything in Java, I would recommend going through the Oracle docs before reading any book, http://docs.oracle.com/javase/tutorial/java/javaOO/nested.html

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   • What are the differences between calling System.exit(0) and Thread.currentThread().interrupt() in the main thread of a Java program?

     Top Answer

     Answered Dec 10, 2014 · 44 votes

     Summary

     • thread.interrupt() does not stop a thread. It is used for coordination in multi-threaded programs. Don't use it unless you know exactly what you do.
     • Throwing a RuntimeException will (usually) terminate the thread but not necessarily the program.
     • System.exit(int) almost always terminates the program and returns a status code.
     • In unusual situations, System.exit(int) might not actually stop the program. Runtime.getRuntime().halt(int) on the other hand, always does.

     Thread Interruption

     I'm afraid your first sentence is wrong. Thread.currentThread().interrupt() does not stop the thread or the program.

     Interrupting a thread is a way to signal that it should stop, but this is a cooperative effort: The code in the thread is supposed to check the interrupted status from time to time and (in most cases - but even this is only optional) should stop if is has been interrupted. If it doesn't do that nothing will happen.

     Specifically, interrupting a thread (any thread, include the currently executing one) will only set the interrupted flag. Certain methods in the standard library will throw an InterruptedException, but this is also just a way to signal that the thread has been interrupted. What should be done in such a situation is up to the code running in that thread.

     Here are the relevant parts from the Java Concurrency in Practice book by Brian Goetz:

     Thread provides the interrupt method for interrupting a thread and for querying whether a thread has been interrupted. Each thread has a boolean property that represents its interrupted status; interrupting a thread sets this status.

     Interruption is a cooperative mechanism. One thread cannot force another to stop what it is doing and do something else; when thread A interrupts thread B, A is merely requesting that B stop what it is doing when it gets to a convenient stopping point if it feels like it.While there is nothing in the API or language specification that demands any specific application level semantics for interruption, the most sensible use for interruption is to cancel an activity. Blocking methods that are responsive to interruption make it easier to cancel long running activities on a timely basis.

     Exceptions and System.exit(int)

     The Javadoc of System.exit(int)

     says:

     Terminates the currently running Java Virtual Machine. The argument serves as a status code; by convention, a nonzero status code indicates abnormal termination.

     So calling exit() will (almost) definitely stop your program. In contrast to throwing a RuntimeException (or an Error), this can not be caught somewhere down the call stack and it does also not depend on whether there are other threads running. On the other hand, an uncaught exception terminates the thread in which it was thrown, but if there are any other (non-daemon) threads, the program will continue to run.

     Another difference to throwing an Exception is that exit() will not print anything to the console (as does an uncaught exception) but instead makes the program return a specific status code. Status codes are sometimes used in shell or batch scripts but other than that, they are not very useful.

     Runtime.halt(int)

     Finally (for completeness' sake), I'd like to point out a third possibility to exit a Java program. When System.exit(int) is called (or the program ends in some other way), the runtime does some cleanup work before the Java Virtual Machine is halted. This is described in the Javadoc of Runtime.exit(int) (which is called by System.exit(int):

     The virtual machine's shutdown sequence consists of two phases. In the first phase all registered shutdown hooks, if any, are started in some unspecified order and allowed to run concurrently until they finish. In the second phase all uninvoked finalizers are run if finalization-on-exit has been enabled. Once this is done the virtual machine halts.

     If any shutdown hook or finalizer is prevented from completing, for example because of a deadlock, the program might never actually exit. The only method that guarantees that the JVM halts is Runtime.halt(int):

     This method should be used with extreme caution. Unlike the exit method, this method does not cause shutdown hooks to be started and does not run uninvoked finalizers if finalization-on-exit has been enabled.

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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

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   Apr 9, 2023 · The java.util.Dictionary class in Java is an abstract class that represents a collection of key-value pairs, where keys are unique and are used to access the values. It was part of the Java Collections Framework introduced in Java 1.2 but has been largely replaced by the java.util.Map interface since Java 1.2.

3. www.javatpoint.com › dictionary-class-in-javaDictionary Class in Java - Javatpoint

   www.javatpoint.com › dictionary-class-in-java

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   In Java, Dictionary is the list of key-value pairs. We can store, retrieve, remove, get, and put values in the dictionary by using the Java Dictionary class. In this section, we will discuss the Java Dictionary class that stores data in key-value pairs just like the Map interface.

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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   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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   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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   Why is the Dictionary class no longer used in Java?

   • According to Java documentation, the Dictionary class is no longer in use because it is outdated. Instead of the Dictionary class, the HashMap class is used. Since we can say that HashMap is a type of dictionary.

   Dictionary Class in Java - Javatpoint

   www.javatpoint.com/dictionary-class-in-java

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5. thelinuxcode.com › create-a-dictionary-in-javaThe Complete Guide to Effectively Using Dictionaries in Java

   thelinuxcode.com › create-a-dictionary-in-java

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   Dec 27, 2023 · Dictionaries are a fundamental data structure in programming used to map keys to values for efficient lookup and organization. Mastering dictionaries is key to writing optimized Java code. In this comprehensive guide, you‘ll learn all about dictionaries and how to leverage them in your Java programs like a pro! We‘ll cover: What dictionaries are and … The Complete Guide to Effectively ...

6. docs.oracle.com › java › utilDictionary (Java SE 21 & JDK 21) - docs.oracle.com

   docs.oracle.com › java › util

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   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.

7. docs.oracle.com › util › class-useUses of Class java.util.Dictionary (Java Platform SE 8 ) - Oracle

   docs.oracle.com › util › class-use

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   Packages that use Dictionary. Package. 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 ...

8. thelinuxcode.com › java-dictionaryAn In-Depth Guide to Using Dictionaries in Java – TheLinuxCode

   thelinuxcode.com › java-dictionary

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   Nov 8, 2023 · Dictionaries are a critical data structure in many programming languages, allowing you to store and retrieve data as key-value pairs. In Java, the Dictionary abstract class provides a useful implementation of a hash table-backed dictionary. In this comprehensive guide, we‘ll cover everything you need to effectively use dictionaries in your Java applications. What is a … An In-Depth Guide ...

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

   ioflood.com › blog › java-dictionary

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   Nov 9, 2023 · Think of Java’s HashMaps and Hashtables as a real-world dictionary, allowing us to store and retrieve data based on unique keys. These tools are incredibly versatile and handy for various tasks. This guide will walk you through the creation, usage, and manipulation of dictionaries in Java.