Java Collection Framework---generic summary

/* Generics: Specify the collection type to identify problems at run time rather than compile time, eliminating security risks. Avoid strong turns.  */package pack;import Java.util.arraylist;import Java.util.iterator;/*public class Main {public static void Sys (Object    obj) {System.out.println (obj); } public static void Main (string[] args) {treeset<string> Al = new Treeset<string> (New Mycomparator  ());        Set generic Al.add ("AA");        Al.add ("BBB");        Al.add ("C");        Iterator<string> it = Al.iterator ();  while (It.hasnext ()) {String s = (string) it.next ();            Avoid strong-turn SYS (s);        SYS (It.next ()); }}}class Mycomparator implements comparator<string> {public int compare (String o1,string O2) {int a        = new Integer (O2.length ()). CompareTo (New Integer (O1.length ()));        if (a==0) {return O2.compareto (O1);    } return A; }}*//*public class Main {public static void Main (string[] args) {demo<integer> d = new DEMO&LT;INTEGER&G        t; (); D.show (4);        D.show (New Integer (5));        demo<string> D1 = new demo<string> ();    D1.show ("haha");    }}class demo<t> {//generic method, currently undefined what type public void Show (T t) {System.out.println (t); }}*//*interface inter<t> {//generic interface void Show (T-t);}    Class Demo<t> implements inter<t> {public void show (T t) {System.out.println (t); }}public class Main {public static void Main (string[] args) {demo<integer> d = new demo<integer> ()        ;    D.show (New Integer (3)); }}*/public class Main {public static void Main (string[] args) {arraylist<string> al1 = new arraylist<        String> ();        Al1.add ("JAVA1");        Al1.add ("Java2");        Al1.add ("Java3");        arraylist<integer> Al2 = new arraylist<integer> ();        Al2.add (1);        Al2.add (2);        Al2.add (3);        Show (AL1);    Show (AL2); } public static <T> void Show (Arraylist<t> a) {//t can be used? Replace       Iterator<t> it = A.iterator ();        while (It.hasnext ()) {System.out.println (It.next ()); }    }}

Java Collection Framework---generic summary