The best new features in Java 25

class Shape {
    final int area;
    public Shape(int area) {
        if (area <= 0) throw new IllegalArgumentException("Area must be positive.");
        this.area = area;
    }
}

Now say you want to have a Rectangle class. In Java before JDK 25, you’d have to somehow extract the calculation to use it in the super() call, usually using a static method:

// The old way
class Rectangle extends Shape {
    private static int checkAndCalcArea(int w, int h) {
        if (w <= 0 || h <= 0) {
            throw new IllegalArgumentException("Dimensions must be positive.");
        }
        return w * h;
    }

    public Rectangle(int width, int height) {
        super(checkAndCalcArea(width, height)); // super() had to be first
        // ... constructor logic ...
    }
}

This code is quite clunky. But in Java 25, it’s easier to follow your intention, and run the area calculation in the Rectangle constructor:

class Rectangle extends Shape {
    final int width;
    final int height;

    public Rectangle(int width, int height) {
        if (width <= 0 || height <= 0) {
            throw new IllegalArgumentException("Dimensions must be positive.");
        }
        int area = width * height;

        super(area); // Before 25, this was an error

        this.width = width;
        this.height = height;
    }
}

Wholesale module imports

Another feature finalized in JDK 25, JEP 511: Module import declarations, lets you import an entire module instead of having to import each package one by one.