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‎src/generics/E21_ClassTypeCapture.java‎

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package generics;
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import java.util.HashMap;
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import java.util.Map;
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import static net.mindview.util.Print.*;
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//: generics/ClassTypeCapture.java
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class ClassTypeCapture2 {
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Map<String, Class<?>> types = new HashMap<String, Class<?>>();
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public Object createNew(String typename) {
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Class<?> cl = types.get(typename);
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try {
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return cl.newInstance();
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} catch (NullPointerException e) {
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// TODO Auto-generated catch block
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// e.printStackTrace();
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print("Not a registered typename: "+typename);
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} catch (IllegalAccessException e) {
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// TODO Auto-generated catch block
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e.printStackTrace();
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} catch (InstantiationException e) {
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// TODO Auto-generated catch block
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e.printStackTrace();
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}
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return null;
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}
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public void addType(String typename, Class<?> kind) {
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types.put(typename, kind);
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}
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}
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public class E21_ClassTypeCapture<T> {
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public static void main(String[] args) {
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ClassTypeCapture2 ctt = new ClassTypeCapture2();
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ctt.addType("Building", Building.class);
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ctt.addType("House", House.class);
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ctt.addType("Product", Product.class);
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print(ctt.createNew("Building").getClass());
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print(ctt.createNew("House").getClass());
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// Product类没有无参构造器
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ctt.createNew("Product");
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ctt.createNew("Car");
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}
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} /* Output:
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class generics.Building
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class generics.House
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java.lang.InstantiationException: generics.Product
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at java.lang.Class.newInstance(Class.java:364)
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at generics.ClassTypeCapture2.createNew(E21_ClassTypeCapture.java:13)
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at generics.E21_ClassTypeCapture.main(E21_ClassTypeCapture.java:39)
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Not a registered typename: Car
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*///:~

‎src/generics/Store.java‎

Lines changed: 69 additions & 64 deletions
Original file line numberDiff line numberDiff line change
@@ -1,79 +1,84 @@
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package generics;
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//: generics/Store.java
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// Building up a complex model using generic containers.
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import java.util.*;
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import net.mindview.util.*;
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class Product {
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private final int id;
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private String description;
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private double price;
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public Product(int IDnumber, String descr, double price){
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id = IDnumber;
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description = descr;
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this.price = price;
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System.out.println(toString());
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}
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public String toString() {
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return id + ": " + description + ", price: $" + price;
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}
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public void priceChange(double change) {
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price += change;
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}
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public static Generator<Product> generator =
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new Generator<Product>() {
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private Random rand = new Random(47);
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public Product next() {
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return new Product(rand.nextInt(1000), "Test",
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Math.round(rand.nextDouble() * 1000.0) + 0.99);
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}
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};
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private final int id;
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private String description;
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private double price;
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public Product(int IDnumber, String descr, double price) {
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id = IDnumber;
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description = descr;
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this.price = price;
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System.out.println(toString());
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}
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public String toString() {
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return id + ": " + description + ", price: $" + price;
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}
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public void priceChange(double change) {
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price += change;
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}
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public static Generator<Product> generator = new Generator<Product>() {
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private Random rand = new Random(47);
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public Product next() {
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return new Product(rand.nextInt(1000), "Test", Math.round(rand
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.nextDouble() * 1000.0) + 0.99);
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}
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};
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}
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class Shelf extends ArrayList<Product> {
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public Shelf(int nProducts) {
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Generators.fill(this, Product.generator, nProducts);
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}
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}
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public Shelf(int nProducts) {
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Generators.fill(this, Product.generator, nProducts);
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}
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}
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class Aisle extends ArrayList<Shelf> {
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public Aisle(int nShelves, int nProducts) {
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for(int i = 0; i < nShelves; i++)
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add(new Shelf(nProducts));
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}
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public Aisle(int nShelves, int nProducts) {
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for (int i = 0; i < nShelves; i++)
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add(new Shelf(nProducts));
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}
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}
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class CheckoutStand {}
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class Office {}
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class CheckoutStand {
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}
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class Office {
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}
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public class Store extends ArrayList<Aisle> {
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private ArrayList<CheckoutStand> checkouts =
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new ArrayList<CheckoutStand>();
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private Office office = new Office();
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public Store(int nAisles, int nShelves, int nProducts) {
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for(int i = 0; i < nAisles; i++)
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add(new Aisle(nShelves, nProducts));
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}
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public String toString() {
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StringBuilder result = new StringBuilder();
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for(Aisle a : this)
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for(Shelf s : a)
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for(Product p : s) {
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result.append(p);
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result.append("\n");
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}
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return result.toString();
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}
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public static void main(String[] args) {
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System.out.println(new Store(14, 5, 10));
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}
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} /* Output:
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258: Test, price: $400.99
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861: Test, price: $160.99
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868: Test, price: $417.99
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207: Test, price: $268.99
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551: Test, price: $114.99
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278: Test, price: $804.99
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520: Test, price: $554.99
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140: Test, price: $530.99
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...
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*///:~
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private ArrayList<CheckoutStand> checkouts = new ArrayList<CheckoutStand>();
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private Office office = new Office();
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public Store(int nAisles, int nShelves, int nProducts) {
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for (int i = 0; i < nAisles; i++)
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add(new Aisle(nShelves, nProducts));
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}
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public String toString() {
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StringBuilder result = new StringBuilder();
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for (Aisle a : this)
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for (Shelf s : a)
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for (Product p : s) {
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result.append(p);
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result.append("\n");
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}
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return result.toString();
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}
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public static void main(String[] args) {
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System.out.println(new Store(14, 5, 10));
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}
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} /*
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* Output: 258: Test, price: $400.99 861: Test, price: $160.99 868: Test, price:
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* $417.99 207: Test, price: $268.99 551: Test, price: $114.99 278: Test, price:
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* $804.99 520: Test, price: $554.99 140: Test, price: $530.99 ...
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*/// :~

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