Copy cat > /tmp/Lab13.java << 'JAVAEOF'
import java.util.*;
import java.util.function.*;
import java.util.stream.*;
public class Lab13 {
interface Priceable {
double getPrice();
default double withTax(double rate) { return getPrice() * (1 + rate); }
default double withDiscount(double pct) { return getPrice() * (1 - pct); }
default String formatted() { return String.format("$%.2f", getPrice()); }
static Priceable of(double price) { return () -> price; }
private double bounded(double min, double max) {
double p = getPrice(); return Math.max(min, Math.min(max, p)); }
default double clamp(double min, double max) { return bounded(min, max); }
}
interface Discountable { double getDiscount(); default double netPrice(double base) { return base * (1 - getDiscount()); } }
interface Taxable { double getTaxRate(); default double grossPrice(double base) { return base * (1 + getTaxRate()); } }
static class ProductListing implements Priceable, Discountable, Taxable {
private final String name; private final double price, discount, taxRate;
ProductListing(String name, double price, double discount, double taxRate) {
this.name=name; this.price=price; this.discount=discount; this.taxRate=taxRate; }
@Override public double getPrice() { return price; }
@Override public double getDiscount() { return discount; }
@Override public double getTaxRate() { return taxRate; }
double finalPrice() { return grossPrice(netPrice(price)); }
@Override public String toString() {
return String.format("%s: base=%s disc=%.0f%% tax=%.0f%% final=$%.2f",
name, formatted(), discount*100, taxRate*100, finalPrice()); }
}
@FunctionalInterface interface Transformer<T> {
T transform(T input);
default Transformer<T> andThen(Transformer<T> next) { return v -> next.transform(transform(v)); }
static <T> Transformer<T> identity() { return v -> v; }
}
interface Exportable { String toJson(); }
interface Archivable extends Exportable { String archive(); }
record Product(int id, String name, double price, int stock) implements Archivable {
@Override public String toJson() {
return "{\"id\":%d,\"name\":\"%s\",\"price\":%.2f}".formatted(id,name,price); }
@Override public String archive() { return "ARCHIVE:" + toJson(); }
}
interface ReportGenerator {
List<String> getHeaders();
List<List<String>> getRows();
String getSeparator();
default String generate() {
var sb = new StringBuilder();
sb.append(String.join(getSeparator(), getHeaders())).append("\n");
sb.append("-".repeat(50)).append("\n");
getRows().forEach(row -> sb.append(String.join(getSeparator(), row)).append("\n"));
return sb.toString();
}
}
public static void main(String[] args) {
System.out.println("=== Interface Default Methods ===");
var listings = List.of(
new ProductListing("Surface Pro", 864.0, 0.10, 0.08),
new ProductListing("Surface Pen", 49.99, 0.05, 0.08),
new ProductListing("Office 365", 99.99, 0.00, 0.08));
listings.forEach(l -> System.out.println(" " + l));
Priceable p = Priceable.of(864.0);
System.out.printf("%nPriceable.of(864): %s +tax=$%.2f clamped=[50,500]: $%.0f%n",
p.formatted(), p.withTax(0.08), p.clamp(50, 500));
System.out.println("\n=== Transformer Composition ===");
Transformer<Double> applyDiscount = price -> price * 0.90;
Transformer<Double> applyTax = price -> price * 1.08;
Transformer<Double> round2dp = price -> Math.round(price * 100) / 100.0;
Transformer<Double> pipeline = applyDiscount.andThen(applyTax).andThen(round2dp);
for (double base : List.of(864.0, 49.99, 99.99, 29.99)) {
System.out.printf(" $%-8.2f -> disc->tax->round -> $%.2f%n", base, pipeline.transform(base));
}
System.out.println("\n=== Interface Hierarchy ===");
List<Object> items = List.of(
new Product(1, "Surface Pro", 864.0, 15),
new Product(2, "Surface Pen", 49.99, 80),
"just a string");
for (var item : items) {
System.out.print(" " + item.getClass().getSimpleName() + ": ");
if (item instanceof Archivable a) System.out.println(a.archive());
else if (item instanceof Exportable e) System.out.println(e.toJson());
else System.out.println(item);
}
System.out.println("\n=== Template Method via Default ===");
ReportGenerator csvReport = new ReportGenerator() {
public List<String> getHeaders() { return List.of("Name","Price","Disc%","Final"); }
public String getSeparator() { return ","; }
public List<List<String>> getRows() {
return listings.stream().map(l -> List.of(
l.name, l.formatted(), (int)(l.discount*100) + "%", String.format("$%.2f", l.finalPrice()))).toList();
}
};
System.out.println(csvReport.generate());
}
}
JAVAEOF
docker run --rm -v /tmp/Lab13.java:/tmp/Lab13.java zchencow/innozverse-java:latest sh -c "javac /tmp/Lab13.java -d /tmp && java -cp /tmp Lab13" 