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Task/Abstract-type/Apex/abstract-type.apex

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+// Interface
+public interface PurchaseOrder {
+    // All other functionality excluded
+    Double discount();
+}
+
+// One implementation of the interface for customers
+public class CustomerPurchaseOrder implements PurchaseOrder {
+    public Double discount() {
+        return .05;  // Flat 5% discount
+    }
+}
+
+
+// Abstract Class
+public abstract class AbstractExampleClass {
+	protected abstract Integer abstractMethod();
+}
+
+// Complete the abstract class by implementing its abstract method
+public class Class1 extends AbstractExampleClass {
+	public override Integer abstractMethod() { return 5; }
+}