集合类接口和类层次关系图

1. Collection vs Collections

首先，“Collection”和“Collections”是两个不同的概念。你可以从下面的层次关系图中看到，”Collection”是集合层次的顶层接口，而”Collections”是提供了操作集合类型的静态方法的类。

2. 集合类层次关系图

下图是集合类的层次关系图

3. Map的类层次结构关系图

下图是Map的类层次结构关系图

4. 集合类总结

5. 代码示例

下面是一个简单的集合的例子：

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List a1 = new ArrayList(); a1.add("Program"); a1.add("Creek"); a1.add("Java"); a1.add("Java"); System.out.println("ArrayList Elements"); System.out.print(" " + a1 + " ");   List l1 = new LinkedList(); l1.add("Program"); l1.add("Creek"); l1.add("Java"); l1.add("Java"); System.out.println("LinkedList Elements"); System.out.print(" " + l1 + " ");   Set s1 = new HashSet(); // or new TreeSet() will order the elements; s1.add("Program"); s1.add("Creek"); s1.add("Java"); s1.add("Java"); s1.add("tutorial"); System.out.println("Set Elements"); System.out.print(" " + s1 + " ");   Map m1 = new HashMap(); // or new TreeMap() will order based on keys m1.put("Windows", "2000"); m1.put("Windows", "XP"); m1.put("Language", "Java"); m1.put("Website", "programcreek.com"); System.out.println("Map Elements"); System.out.print(" " + m1);

输出:

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ArrayList Elements     [Program, Creek, Java, Java] LinkedList Elements     [Program, Creek, Java, Java] Set Elements     [tutorial, Creek, Program, Java] Map Elements     {Windows=XP, Website=programcreek.com, Language=Java}