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Date/Time Beginner

Locale constructors to Locale.of()

Create language and region locales with Locale.of() instead of deprecated constructors.

Code Comparison

✕ Deprecated constructor

Locale brazilianPortuguese =
    new Locale("pt", "BR");

✓ Java 19+

Locale brazilianPortuguese =
    Locale.of("pt", "BR");

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Why the modern way wins

✅

Supported API

Avoids deprecated constructors.

👁

Clear construction

The named factory communicates intent.

🧩

Consistent style

Matches modern JDK value-object factories.

Old Approach

Locale constructors

Modern Approach

Locale.of()

Since JDK

Difficulty

Beginner

JDK Support

Locale constructors to Locale.of()

Available

Available since JDK 19 (September 2022)

How it works

Locale factory methods replace constructors deprecated in JDK 19. The factory form is clearer, aligns with other value-based APIs, and centralizes locale creation.

Date formatting

Pre-Java 8

// Not thread-safe!
SimpleDateFormat sdf =
    new SimpleDateFormat("yyyy-MM-dd");
String formatted = sdf.format(date);
// Must synchronize for concurrent use

Java 8+

DateTimeFormatter fmt =
    DateTimeFormatter.ofPattern(
        "uuuu-MM-dd");
String formatted =
    LocalDate.now().format(fmt);
// Thread-safe, immutable

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JDK 8+ →

Date/Time Beginner

java.time API basics

Pre-Java 8

// Mutable, confusing, zero-indexed months
Calendar cal = Calendar.getInstance();
cal.set(2025, 0, 15); // January = 0!
Date date = cal.getTime();
// not thread-safe

Java 8+

LocalDate date = LocalDate.of(
    2025, Month.JANUARY, 15);
LocalTime time = LocalTime.of(14, 30);
Instant now = Instant.now();
// immutable, thread-safe

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JDK 8+ →

Strings Beginner

String.formatted()

Java 8

String msg = String.format(
    "Hello %s, you are %d",
    name, age
);

Java 15+

String msg =
    "Hello %s, you are %d"
    .formatted(name, age);

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JDK 15+ →