Recommended Java notation

1. For loop

         // 1          for (int i = 0; i < list.size (); i++) {            int item = list.get (i);            System.out.println ("This is the first" + (i+1) + "A: Value:" + Item);        }         // 2        int j = 0;          for (int  i:list) {            + +J;            System.out.println ("This is the first" + j + ": Value:" + i);        }

Recommended notation 2

2. HashMap traversal

    map<string,string> map=New hashmap<string,string>();        Map.put ("1", "value1");        Map.put ("2", "value2");        Map.put ("3", "Value3");        Map.put ("4", "Value4");
     // the third type: recommended, especially when the  capacity is large        System.out.println ("\ n traverse key and value through Map.entryset")          ;  for (map.entry<string, string> entry:map.entrySet ())        {         System.out.println ("Key:" + entry.getkey () + "Value:" +Entry.getvalue ());        }

3. How to output the stack information of Printstacktrace () when using log4j

Log.error (E.getmessage (), E)

4. String concatenation

StringBuilder tmpstr== tmpstr.tostring ();

Recommended Java notation