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Language Beginner

Records for data classes

One line replaces 30+ lines of boilerplate for immutable data carriers.

Records

Code Comparison

✕ Java 8

public class Point {
    private final int x, y;
    public Point(int x, int y) { ... }
    public int getX() { return x; }
    public int getY() { return y; }
    // equals, hashCode, toString
}

✓ Java 16+

public record Point(int x, int y) {}

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Why the modern way wins

⚡

One-line definition

A single line replaces constructor, getters, equals, hashCode, toString.

🔒

Immutable by default

All fields are final — no setter footguns.

🧩

Pattern-friendly

Records work with destructuring patterns in switch and instanceof.

Old Approach

Verbose POJO

Modern Approach

record

Since JDK

Difficulty

Beginner

JDK Support

Records for data classes

Available

Widely available since JDK 16 (March 2021)

How it works

Records automatically generate the constructor, accessors (x(), y()), equals(), hashCode(), and toString(). They are immutable by design and ideal for DTOs, value objects, and pattern matching.

Flexible constructor bodies

Java 8

class Square extends Shape {
    Square(double side) {
        super(side, side);
        // can't validate BEFORE super!
        if (side <= 0)
            throw new IAE("bad");
    }
}

Java 25+

class Square extends Shape {
    Square(double side) {
        if (side <= 0)
            throw new IAE("bad");
        super(side, side);
    }
}

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Language Intermediate

Private interface methods

Java 8

interface Logger {
    default void logInfo(String msg) {
        System.out.println(
            "[INFO] " + timestamp() + msg);
    }
    default void logWarn(String msg) {
        System.out.println(
            "[WARN] " + timestamp() + msg);
    }
}

Java 9+

interface Logger {
    private String format(String lvl, String msg) {
        return "[" + lvl + "] " + timestamp() + msg;
    }
    default void logInfo(String msg) {
        IO.println(format("INFO", msg));
    }
    default void logWarn(String msg) {
        IO.println(format("WARN", msg));
    }
}

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JDK 9+ →

Language Intermediate

Pattern matching in switch

Java 8

String format(Object obj) {
    if (obj instanceof Integer i)
        return "int: " + i;
    else if (obj instanceof Double d)
        return "double: " + d;
    else if (obj instanceof String s)
        return "str: " + s;
    return "unknown";
}

Java 21+

String format(Object obj) {
    return switch (obj) {
        case Integer i -> "int: " + i;
        case Double d  -> "double: " + d;
        case String s  -> "str: " + s;
        default        -> "unknown";
    };
}

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JDK 21+ →