Uma classe que simula um programa estruturado para calcular areas geometricas

Areas.java

import java.util.Scanner;

public class Areas {
    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        double a = scan.nextDouble();
        double b = scan.nextDouble();
        double c = scan.nextDouble();
        scan.nextLine();
        scan.close();

        print("TRIANGULO", triangulo(a, c));
        print("CIRCULO", circulo(c));
        print("TRAPEZIO", trapezio(a, b, c));
        print("QUADRADO", quadrado(b));
        print("RETANGULO", retangulo(a, b));
    }

    public static void print (String title, double value) {
        System.out.printf("%s: %.3f%n", title, value);
    }

    public static double triangulo (double b, double h) {
        return b*h/2;
    }

    public static double circulo (double r) {
        double pi = 3.14159;
        return pi * Math.pow(r, 2.0);
    }

    public static double trapezio (double b, double B, double h) {
        return (b + B) * h/2;
    }

    public static double quadrado (double b) {
        return Math.pow(b, 2.0);
    }

    public static double retangulo (double b, double h) {
        return b * h;
    }
}