//1 add方法
collections.add("java");
collections.add("c");
//2 addAll
Collection<String> collections2 = new ArrayList<String>();
collections2.add("php");
collections2.add("javaScript");
collections2.add("c++");
collections.addAll(collections2);
System.out.println(collections);
//3 contains
boolean res = collections.contains("c");
System.out.println(res);
//4 containsAll
Collection<String> collections3 = new ArrayList<String>();
collections3.add("c");
collections3.add("phx");
System.out.println(collections.containsAll(collections3));
//5 clear
collections3.clear();
//6 isEmpty
System.out.println(collections3.isEmpty());
//7 remove
System.out.println(collections);//[]
collections.remove("java");
System.out.println(collections);
//8 retainAll
collections.retainAll(collections2);
System.out.println(collections);
//9 size
System.out.println(collections.size());
//10 toArray
Object[] objs =collections.toArray();
/*
如果这里强制类型转化时，向下造型会发生ClassCastException
*/
System.out.println(Arrays.toString(objs));
}
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