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cat > /tmp/Lab08.java << 'JAVAEOF'
import java.util.*;
import java.util.function.*;
public class Lab08 {
// 1. Builder
static class Order {
private final int id; private final String product; private final int qty;
private final double price; private final String email; private final String region;
private final boolean express; private final String coupon;
private Order(Builder b) {
this.id=b.id; this.product=b.product; this.qty=b.qty; this.price=b.price;
this.email=b.email; this.region=b.region; this.express=b.express; this.coupon=b.coupon;
}
double total() { return price * qty * (express ? 1.05 : 1.0); }
@Override public String toString() {
return String.format("Order#%d: %dx%s $%.2f email=%s region=%s express=%b coupon=%s",
id, qty, product, total(), email, region, express, coupon);
}
static class Builder {
private final int id; private final String product; private int qty = 1;
private double price; private String email = ""; private String region = "US";
private boolean express = false; private String coupon = null;
Builder(int id, String product, double price) { this.id=id; this.product=product; this.price=price; }
Builder qty(int q) { this.qty = q; return this; }
Builder email(String e) { this.email = e; return this; }
Builder region(String r) { this.region = r; return this; }
Builder express() { this.express = true; return this; }
Builder coupon(String c) { this.coupon = c; return this; }
Order build() {
if (qty <= 0) throw new IllegalStateException("qty must be > 0");
return new Order(this);
}
}
}
// 2. Factory Method
interface Shipper { String ship(String product, String address); String name(); }
static class FedEx implements Shipper {
public String ship(String p, String a) { return "FedEx#FX" + Math.abs(p.hashCode()%1000) + " -> " + a; }
public String name() { return "FedEx"; }
}
static class UPS implements Shipper {
public String ship(String p, String a) { return "UPS#1Z" + Math.abs(p.hashCode()%9999) + " -> " + a; }
public String name() { return "UPS"; }
}
static class ShipperFactory {
private static final Map<String, Supplier<Shipper>> registry =
Map.of("fedex", FedEx::new, "ups", UPS::new);
static Shipper create(String type) {
var s = registry.get(type.toLowerCase());
if (s == null) throw new IllegalArgumentException("Unknown shipper: " + type);
return s.get();
}
}
// 3. Observer (Event Bus)
interface EventListener<T> { void onEvent(String type, T data); }
static class EventBus<T> {
private final Map<String, List<EventListener<T>>> listeners = new HashMap<>();
void on(String event, EventListener<T> l) { listeners.computeIfAbsent(event, k -> new ArrayList<>()).add(l); }
void emit(String event, T data) { listeners.getOrDefault(event, List.of()).forEach(l -> l.onEvent(event, data)); }
}
// 4. Strategy
interface PricingStrategy { double apply(double basePrice, int qty); String label(); }
static PricingStrategy standard() { return new PricingStrategy() {
public double apply(double p, int q) { return p * q; }
public String label() { return "Standard"; } }; }
static PricingStrategy bulk(int threshold, double discount) { return new PricingStrategy() {
public double apply(double p, int q) { return p * q * (q >= threshold ? (1-discount) : 1.0); }
public String label() { return "Bulk(>=" + threshold + "@-" + (int)(discount*100) + "%)"; } }; }
static PricingStrategy tiered() { return new PricingStrategy() {
public double apply(double p, int q) {
if (q >= 100) return p * q * 0.70;
if (q >= 50) return p * q * 0.80;
if (q >= 10) return p * q * 0.90;
return p * q;
}
public String label() { return "Tiered"; } }; }
public static void main(String[] args) {
System.out.println("=== Builder ===");
var o1 = new Order.Builder(1001, "Surface Pro", 864.0)
.qty(2).email("[email protected]").region("US").express().build();
var o2 = new Order.Builder(1002, "Surface Pen", 49.99)
.qty(5).email("[email protected]").coupon("SAVE10").build();
System.out.println(o1);
System.out.println(o2);
System.out.println("\n=== Factory ===");
for (String type : List.of("fedex", "ups")) {
var shipper = ShipperFactory.create(type);
System.out.println(shipper.ship("Surface Pro", "Claymont DE 19703"));
}
System.out.println("\n=== Observer ===");
var bus = new EventBus<Order>();
bus.on("order.placed", (t, o) -> System.out.println(" [Email] Confirmation for " + o.email));
bus.on("order.placed", (t, o) -> System.out.println(" [Inv] Deducted " + o.qty + "x " + o.product));
bus.on("order.express", (t, o) -> System.out.println(" [Ship] Rush processing: " + o.product));
bus.emit("order.placed", o1);
if (o1.express) bus.emit("order.express", o1);
bus.emit("order.placed", o2);
System.out.println("\n=== Strategy ===");
var strategies = List.of(standard(), bulk(10, 0.15), tiered());
for (int qty : List.of(1, 10, 50, 100)) {
strategies.forEach(s ->
System.out.printf(" qty=%-3d %-25s $%,.2f%n", qty, s.label(), s.apply(49.99, qty)));
System.out.println();
}
}
}
JAVAEOF
docker run --rm -v /tmp/Lab08.java:/tmp/Lab08.java zchencow/innozverse-java:latest sh -c "javac /tmp/Lab08.java -d /tmp && java -cp /tmp Lab08"=== Builder ===
Order#1001: 2xSurface Pro $1814.40 [email protected] region=US express=true coupon=null
Order#1002: 5xSurface Pen $249.95 [email protected] region=US express=false coupon=SAVE10
=== Factory ===
FedEx#FX... -> Claymont DE 19703
UPS#1Z... -> Claymont DE 19703
=== Observer ===
[Email] Confirmation for [email protected]
[Inv] Deducted 2x Surface Pro
[Ship] Rush processing: Surface Pro
[Email] Confirmation for [email protected]
[Inv] Deducted 5x Surface Pen
=== Strategy ===
qty=10 Standard $499.90
qty=10 Bulk(>=10@-15%) $424.92
qty=10 Tiered $449.91