java例程练习（泛型和自动打包、解包）

//TestArsgWords.java import java.util.*; public class TestArgsWords { public static void main(String[] args) { Map<String, Integer> m = new HashMap<String, Integer>(); for(int i = 0; i < args.length; i++) { if(!m.containsKey(args[i])) { m.put(args[i], 1); } else { int freq = m.get(args[i]); m.put(args[i], freq + 1); } } System.out.println (m.size() + " distinct words detected:"); System.out.println(m); } }<pre name="code" class="java">//Test.java import java.util.*; public class Test { public static void main(String[] args) { List<String> c = new ArrayList<String>(); c.add("aaa"); c.add("bbb"); c.add("ccc"); for(int i = 0; i < c.size(); i++) { String s = c.get(i); System.out.println(s); } Collection<String> c2 = new HashSet<String> (); c2.add("aaa"); c2.add("bbb"); c2.add("ccc"); for(Iterator<String> it = c2.iterator(); it.hasNext();) { String s = it.next(); System.out.println(s); } } } class MyName implements Comparable<MyName> { int age; public int compareTo(MyName mn) { if(this.age > mn.age) { return 1; } else if(this.age < mn.age) { return -1; } else { return 0; } } }

<pre name="code" class="java">//Test.java import java.util.*; public class Test { public static void main(String[] args) { Map<String, Integer> m1 = new HashMap<String, Integer>(); Map<String, Integer> m2 = new HashMap<String, Integer>(); m1.put("one", 1); //m1.put("one",new Integer(1)); m1.put("two", 2); //m1.put("two",new Integer(2)); m1.put("three", 3); //m1.put("three",new Integer(3)); m2.put("A", 1); //m2.put("A", new Integer(1)); m2.put("B", 2); //m2.put("B", new Integer(2)); System.out.println(m1.size()); System.out.println(m1.containsKey("one")); System.out.println (m2.containsValue(1)); //(m2.containsValue(new Integer(1))); if(m1.containsKey("two")) { int i = m1.get("two"); //int i =(Integer)m1.get("two"); //int i = ((Integer)m1.get("two")).intValue(); System.out.println(i); } Map<String, Integer> m3 = new HashMap<String, Integer>(m1); m3.putAll(m2); System.out.println(m3); } }