chapter 4

jxxchallenger · jxxchallenger · commit 108fda38f65e · 2019-05-16T22:14:20.000+08:00
diff --git a/src/main/java/com/hkbea/chap4/Dish.java b/src/main/java/com/hkbea/chap4/Dish.java
@@ -0,0 +1,50 @@
+package com.hkbea.chap4;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class Dish {
+
+	private final String name;
+	private final boolean vegetarian;
+	private final int calories;
+	private final Type type;
+
+	public Dish(String name, boolean vegetarian, int calories, Type type) {
+		this.name = name;
+		this.vegetarian = vegetarian;
+		this.calories = calories;
+		this.type = type;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public boolean isVegetarian() {
+		return vegetarian;
+	}
+
+	public int getCalories() {
+		return calories;
+	}
+
+	public Type getType() {
+		return type;
+	}
+
+	public enum Type {
+		MEAT, FISH, OTHER
+	}
+
+	@Override
+	public String toString() {
+		return name;
+	}
+
+	public static final List<Dish> menu = Arrays.asList(new Dish("pork", false, 800, Dish.Type.MEAT),
+			new Dish("beef", false, 700, Dish.Type.MEAT), new Dish("chicken", false, 400, Dish.Type.MEAT),
+			new Dish("french fries", true, 530, Dish.Type.OTHER), new Dish("rice", true, 350, Dish.Type.OTHER),
+			new Dish("season fruit", true, 120, Dish.Type.OTHER), new Dish("pizza", true, 550, Dish.Type.OTHER),
+			new Dish("prawns", false, 400, Dish.Type.FISH), new Dish("salmon", false, 450, Dish.Type.FISH));
+}
diff --git a/src/main/java/com/hkbea/chap4/StreamBasic.java b/src/main/java/com/hkbea/chap4/StreamBasic.java
@@ -0,0 +1,52 @@
+package com.hkbea.chap4;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class StreamBasic {
+
+	public static void main(String[] args) {
+		getLowCaloricDishesNamesInJava7(Dish.menu).forEach(str -> System.out.println(str));
+
+		System.out.println("----------------------------------------");
+		getLowCaloricDishesNamesInJava8(Dish.menu).forEach(System.out::println);
+		
+		List<String> threeHighCaloricDishNames = Dish.menu.parallelStream().filter(dish -> dish.getCalories() > 300).map(Dish::getName).limit(3).collect(Collectors.toList());
+		System.out.println(threeHighCaloricDishNames);
+		//4.4
+		
+		List<String> names = Dish.menu.stream().filter(d -> {
+			System.out.println("filtering " + d.getName());
+			return d.getCalories() > 300;
+		}).map(d -> {
+			System.out.println("mapping " + d.getName());
+			return d.getName();
+		}).limit(3).collect(Collectors.toList());
+		System.out.println(names);
+	}
+	
+	public static List<String> getLowCaloricDishesNamesInJava7(List<Dish> dishes) {
+		List<Dish> lowCaloricDishes = new ArrayList<>();
+		for(Dish dish:dishes) {
+			if(dish.getCalories() < 400) {
+				lowCaloricDishes.add(dish);
+			}
+		}
+		
+		Collections.sort(lowCaloricDishes, Comparator.comparing(Dish::getCalories));
+		
+		List<String> lowCaloricDishesName = new ArrayList<>();
+		for(Dish dish : lowCaloricDishes) {
+			lowCaloricDishesName.add(dish.getName());
+		}
+		return lowCaloricDishesName;
+	}
+	
+	public static List<String> getLowCaloricDishesNamesInJava8(List<Dish> dishes) {
+		return dishes.parallelStream().filter((Dish dish) -> dish.getCalories() < 400).sorted(Comparator.comparing(Dish::getCalories)).map(dish -> dish.getName()).collect(Collectors.toList());
+	}
+
+}
