Learning about Factory Methods and Collections Operations

Java Collections/src/CollectionOperations.java

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+import common.Product;
+
+import java.util.ArrayList;
+import java.util.Collections;
+
+public class CollectionOperations {
+    public static Product door = new Product("Wooden Door", 35);
+    public static Product floorPanel = new Product("Floor Panel", 25);
+    public static Product window = new Product("Glass Window", 10);
+
+    public static void main(String[] args) {
+        var products = new ArrayList<Product>();
+        Collections.addAll(products, door, floorPanel, window);
+
+        System.out.println(Collections.max(products, Product.BY_WEIGHT));
+        System.out.println(Collections.min(products, Product.BY_WEIGHT));
+        Collections.fill(products, null);
+
+        System.out.println("products = " + products);
+
+    }
+}

Java Collections/src/UnmodifiableVsImmutable.java

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+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+public class UnmodifiableVsImmutable {
+    public static void main(String[] args) {
+        Map<String, Integer> mutableCountryToPopulation = new HashMap<>();
+        mutableCountryToPopulation.put("UK", 67);
+        mutableCountryToPopulation.put("USA", 328);
+
+        Map<String, Integer> unmodifiableCountryToPopulation = Collections.unmodifiableMap(mutableCountryToPopulation);
+        Map<String, Integer> copiedCountryToPopulation = Map.copyOf(mutableCountryToPopulation);
+
+        // Throws UnsupportedOperationException: unmodifiableCountryToPopulation.put("Germany", 83);
+        // Throws UnsupportedOperationException: copiedCountryToPopulation.put("Germany", 83);
+
+        System.out.println("copiedCountryToPopulation = " + copiedCountryToPopulation);
+        System.out.println("unmodifiableCountryToPopulation = " + unmodifiableCountryToPopulation);
+        mutableCountryToPopulation.put("Germany", 83);
+        System.out.println("copiedCountryToPopulation = " + copiedCountryToPopulation);
+        System.out.println("unmodifiableCountryToPopulation = " + unmodifiableCountryToPopulation);
+
+        // Short way of constructing a Map
+        var countryToPopulation = Map.of("UK", 67, "USA", 328);
+        // Throws UnsupportedOperationException: countryToPopulation.put("Germany", 83);
+
+    }
+}