Java LocalDateTime: Date and Time Without a Time Zone
Java LocalDateTime examples on Java 25. Create, parse and format date-times, add hours, compare values and convert to ZonedDateTime without DST surprises.
“Core Java” is Sun’s term, used to refer to Java SE, the standard edition and a set of related technologies, like the Java VM, CORBA, etc. This is mostly to differentiate from others like Java ME or Java EE. “Core Java” is Oracle’s definition and refers to subset of Java SE technologies.
The Core Java technologies and application programming interfaces (APIs) are the foundation of the Java Platform, Standard Edition (Java SE). They are used in all classes of Java programming, from desktop applications to Java EE applications.
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Tutorials
Java LocalTime: Time of Day Without a Date (With Examples)
Java LocalTime examples on Java 25. Create, parse and format times, add hours across midnight, check opening hours and measure the time between two times.
Java LocalDate: Create, Parse, Format and Compare Dates
Java LocalDate examples on Java 25. Create, parse and format dates, add days and months, compare dates and convert LocalDate to other date types.
Java Stream Filter with Multiple Conditions: 3 Ways
Java stream filter with multiple conditions using && and ||, chained filter() calls and Predicate and(), or(), negate(), plus dynamic search filters.
Join a Stream of Strings in Java: joining() and String.join()
Join a stream of strings in Java with Collectors.joining() or String.join(), with a delimiter, prefix and suffix, null elements and empty streams.
Java Stream concat(): Merge Streams, Append and Prepend Items
Java Stream concat() merges two streams lazily. Learn to merge many streams, append or prepend items, remove duplicates and concat IntStream on Java 25.
Java Stream: Sort by Multiple Fields With thenComparing()
Sort by multiple fields in a Java stream with comparing() and thenComparing(), mix ascending and descending order, handle nulls and pick keys at runtime.
How to Sort a Stream in Java: Numbers, Strings, Objects, Maps
Learn how to sort a stream in Java by numbers, strings, object fields, descending order and null values, plus sorting map entries and collecting results.
Java Stream to List: toList() vs Collectors.toList()
Convert a Java Stream to List with toList() or Collectors.toList(). Compare modifiability, null items and Java versions, plus ArrayList and IntStream.
Java Stream toArray(): Convert a Stream to an Array
Java Stream toArray() converts a stream to an array. Learn the String[]::new generator, int[] from primitive streams, ArrayStoreException and toList().
Java Stream to Map With Collectors.toMap() Examples
Collect a Java Stream to Map with Collectors.toMap(), handle duplicate keys and null values, and pick LinkedHashMap, TreeMap or an unmodifiable map.
Java Stream Reuse: How to Consume a Stream Multiple Times
Java stream reuse explained with Supplier, collect-once lists, reusable pipeline steps and one-pass collectors like teeing, plus one-shot sources.
Java Stream findFirst() vs findAny(): Differences and Examples
Java Stream findFirst vs findAny explained. findFirst() keeps encounter order, while findAny() may return any element in parallel streams. With null rules.
Java Stream anyMatch(), allMatch() and noneMatch() Examples
Java Stream anyMatch() checks if any element matches a predicate. Learn allMatch(), noneMatch(), empty stream results and short-circuiting with examples.
Java Stream limit() and skip() With Pagination Examples
Java Stream limit() keeps the first n elements and skip() drops them. Learn edge cases, infinite streams, takeWhile() and a pagination helper with code.
Java Stream peek(): How It Works and When It Is Skipped
Java Stream peek() explained with element order, cases where count(), findFirst() and limit() skip it, peek vs map vs forEach, parallel streams and logging
map() vs flatMap() in Java Streams: Difference with Examples
map vs flatMap in Java explained with side-by-side examples, a comparison table, Optional map() vs flatMap(), mapMulti() and when to use each method.
Java Stream flatMap(): Flatten Nested Lists with Examples
Learn Java Stream flatMap() with examples to flatten a list of lists, split lines into words, unwrap Optional values and use flatMapToInt() in Java 25.
Java Stream map(): Transform Elements with Examples
Learn the Java Stream map() method with examples for type conversion, field extraction, DTO mapping, mapToInt(), laziness and map() vs flatMap().
Java Stream max(): Find the Largest Element With a Comparator
Java Stream max() examples with comparators, max by field, ties, empty streams, groups and primitive streams, plus comparators that return wrong results.
Java Stream sorted(): How to Sort a Stream in Java
Java Stream sorted() examples that sort in natural, reverse and custom order with Comparator, records and nulls, plus how it compares with List.sort().
Java Stream filter(): Keep Matching Elements with Examples
Learn the Java Stream filter() method with predicates, lambdas, Predicate.not(), null and map filtering, filter() vs removeIf() and real-world examples.
Java Stream forEach(): Syntax, Examples and Pitfalls
Java Stream forEach() runs an action on every element. See parallel order, forEachOrdered(), shared state, stopping early and checked exceptions.
Secure Random Number Generation in Java with SecureRandom
Secure random number generation in Java with SecureRandom. Create tokens and codes, pick NativePRNG, DRBG or getInstanceStrong and avoid seeding mistakes.
JMeter Tutorial for Beginners: Load Test a REST API
Learn JMeter 5.6.3 step by step: build a test plan with a thread group, HTTP requests, an assertion and think time, run it in CLI mode and read the HTML report.
If-Else Logic in Java Streams: filter, map and partitioningBy
If-else logic in Java streams with filter(), map() with a ternary or switch, partitioningBy(), groupingBy() and Optional, plus a bank statement example
Java forEach(): Iterate a List, Set or Map With Examples
Java forEach() on List, Set and Map with Consumer and BiConsumer, iteration order, forEach vs for loop, break and ConcurrentModificationException
Union of Two Arrays in Java: Set, Stream and Sorted Merge
Find the union of two arrays in Java with LinkedHashSet, IntStream distinct() and a two-pointer merge for sorted input, with order and duplicates covered.
Intersection of Two Arrays in Java, With and Without Duplicates
Find the intersection of two arrays in Java with retainAll(), a HashSet filter, a count map for repeats and two pointers for sorted arrays.
Java Stream Distinct by Multiple Fields (with Examples)
Java Stream distinct by multiple fields with a distinctByKey() predicate, a record key, toMap() or a Gatherer, and why parallel streams change the result.
Java Instance Initializer Block: Order, Rules and Examples
Instance initializer block in Java with examples, covering execution order with fields and constructors, this() chaining, exceptions and double braces.
Java Naming Conventions for Classes, Methods and Variables
Java naming conventions for packages, classes, methods, variables, constants and generics, with identifier rules, examples, a refactoring and style guides.
this vs super in Java: Keywords and Constructor Calls
Learn this and super in Java, this() vs super() constructor calls, Interface.super, Java 25 flexible constructor bodies and static context rules.
Java strictfp Keyword: Why It Is Obsolete Since Java 17
Learn what the strictfp keyword in Java did before Java 17, why JEP 306 made it obsolete, its syntax rules, and how to remove it from old code.
final vs finally vs finalize in Java
Learn the difference between final, finally and finalize in Java, with examples, when finally does not run, and what replaces deprecated finalize().
extends vs implements in Java: Differences With Examples
Learn extends vs implements in Java with examples, a comparison table, using both in one class, interfaces extending interfaces, generics bounds and FAQs.
Java instanceof Operator and Pattern Matching Explained
The Java instanceof operator checks the type of an object. Learn null handling, pattern matching, generics, arrays, switch patterns and isInstance().
throw vs throws in Java: Differences and Examples
throw vs throws in Java compared with a table and examples, plus exception propagation, rethrowing and the throws rules for overriding methods.
Java synchronized Keyword: Methods, Blocks and Locks
Learn the Java synchronized keyword with methods and blocks, which lock each form uses, reentrancy, visibility, deadlocks and virtual threads.
Java try catch finally: Flow, Rules and Examples
Java try catch finally with runnable Java 25 examples, the order the blocks run, multiple catch blocks, return in finally and when finally is skipped.
Java boolean Keyword: Values, Operators and Boolean Class
Learn the Java boolean type, default values, short-circuit operators, the Boolean wrapper, parseBoolean vs getBoolean, and boolean memory size.
Java assert Keyword: Assertions with Examples
Learn the Java assert keyword, enabling assertions with -ea, AssertionError, when to use assert vs exceptions, side effects, and assertions in tests.
Abstract Class in Java: abstract Keyword with Examples
Learn the abstract class in Java with examples, abstract methods, illegal modifier combinations, abstract class vs interface, and sealed hierarchies.
Java Control Flow Statements: Decisions, Loops and Branching
Java control flow statements explained with if-else, switch, for, while, do-while, break, continue and yield, with examples and links to each tutorial.
Java CopyOnWriteArraySet: Thread-Safe Set With Examples
Java CopyOnWriteArraySet explained with examples, snapshot iteration, O(n) costs, a chat room use case and a comparison with ConcurrentHashMap.newKeySet().
Java CopyOnWriteArrayList: Snapshot Iterators and Use Cases
Learn how Java CopyOnWriteArrayList copies its array on writes, why its iterators never fail, addIfAbsent(), Java 21 methods and when to use it.
Java TransferQueue and LinkedTransferQueue with Examples
Java TransferQueue and LinkedTransferQueue explained with transfer(), tryTransfer() and put() examples, timeouts, and a comparison with SynchronousQueue.
Java ArrayBlockingQueue: Bounded Blocking Queue Examples
Java ArrayBlockingQueue examples covering put, offer, take, fairness, producer-consumer threads and batch draining with drainTo(), vs LinkedBlockingQueue.
Java PriorityBlockingQueue: Thread-Safe Priority Queue Examples
Java PriorityBlockingQueue examples with Comparator, take(), drainTo() and a print-server worker, plus how it differs from PriorityQueue and DelayQueue.
Java Priority Queue: PriorityQueue, Comparator and Max-Heap
Java priority queue tutorial with PriorityQueue examples for natural order, Comparator, max-heap, equal priorities and top K, and why it prints unsorted.