Java

Core Java, object oriented programming, collections, multithreading and JDBC.

100 notes in 18 topics

Topics in Java

Java

Optional makes absence part of the type, so a caller cannot forget that a value might not be there.

Java

A stream describes a computation over a sequence of elements. You state what you want, and the pipeline decides how to walk the data.

Java

filter, map, flatMap, sorted, distinct, limit, skip and peek. Each returns a new stream and none of them runs on its own.

Java

A terminal operation runs the pipeline and produces a result, and reduce is the general purpose way to fold a stream into one value.

Java

Collectors turn a stream into a collection, a map or a summary, and grouping is where they become genuinely powerful.

Java

A parallel stream splits the work across threads. It helps less often than people expect, and it breaks silently when the rules are ignored.

Java

The modern date and time API is immutable, thread safe and clearly named, and it replaced the older Date and Calendar classes entirely.

Java

Instant marks a point on the timeline; Duration measures time based amounts and Period measures date based ones.

Java

DateTimeFormatter converts between text and date time values, and ZoneId handles the region rules that make time zones difficult.

Java

Path names a location and Files performs the operations. Together they replaced the older File class for almost every purpose.

Java

InputStream and OutputStream carry raw bytes; Reader and Writer carry characters. Choosing wrongly corrupts data.

Java

Every unbuffered read is a system call. Buffering turns thousands of them into a handful, and it is the single largest I/O win available.