ブルース・エッケルによるロシア語の本 『Javaの哲学（Javaの哲学）』の質問と演習

// Fruit.java public class Fruit { private int weight = 0; public Fruit(int weight) { this.weight = weight; } public void printWeight() { System.out.println("Weight is: " + weight); } } // Apply.java import java.util.*; public class Apply { public static void main(String[] args) { List<Fruit> fruits = Arrays.asList(new Fruit(10), new Fruit(20)); // a System.out.println("Task a: "); for (Fruit f : fruits) { f.printWeight(); } // b System.out.println("Task b: "); Iterator<Fruit> it = fruits.iterator(); while(it.hasNext()) { it.next().printWeight(); } } } 

 import java.util.*; import java.util.Map.Entry; public class Apply { public static void main(String[] args) { //  HashMap,      Map<String, Fruit> fruit = new HashMap<String, Fruit>(); fruit.put("Bob", new Fruit(10)); fruit.put("Mary", new Fruit(20)); //    foreach System.out.println("With foreach"); for (String key : fruit.keySet()) { fruit.get(key).printWeight(); } //     System.out.println("With iterator"); Iterator<Entry<String, Fruit>> it = fruit.entrySet().iterator(); while (it.hasNext()) { it.next().getValue().printWeight(); } } } 

 // StringComparator.java import java.util.Comparator; public class StringComparator implements Comparator<String> { @Override public int compare(String s1, String s2) { if (s1.length() < s2.length()) { return -1; } if(s1.length() > s2.length()) { return 1; } return 0; } } // PriorityQueue.java import java.util.Comparator; import java.util.PriorityQueue; public class PriorityQueueUse { public static void main(String[] args) { Comparator<String> comparator = new StringComparator(); PriorityQueue<String> queue = new PriorityQueue<String>(10, comparator); queue.add("abcde"); queue.add("abc"); queue.add("abcdefghi"); queue.add("a"); //          String System.out.println("Before removing:"); System.out.println(queue); //          String System.out.println(); System.out.println("Look at removing order: "); while (queue.size() != 0) { System.out.println(queue.remove()); } } }