MESSAGE
| DATE | 2016-05-22 |
| FROM | Ruben Safir
|
| SUBJECT | Subject: [Hangout-NYLXS] Fwd: Re: how does one explain this syntax?
|
-------- Forwarded Message --------
Subject: Re: how does one explain this syntax?
Date: Sun, 22 May 2016 08:41:30 -0700
From: Knute Johnson
Organization: A noiseless patient Spider
Newsgroups: comp.lang.java.programmer
References:
On 5/21/2016 22:51, ruben safir wrote:
> This passes for a demonstration and teaching example for a TreeMap
>
>
> import java.util.TreeMap;
> import java.util.Set;
> import java.util.Iterator;
> import java.util.Map;
>
> public class Details {
>
> public static void main(String args[]) {
>
> /* This is how to declare TreeMap */
> TreeMap tmap =
> new TreeMap(); <>
> /*Adding elements to TreeMap*/
> tmap.put(1, "Data1");
> tmap.put(23, "Data2");
> tmap.put(70, "Data3");
> tmap.put(4, "Data4");
> tmap.put(2, "Data5");
>
> /* Display content using Iterator*/
> Set set = tmap.entrySet(); <> constructor for another class?
> Iterator iterator = set.iterator(); <> while(iterator.hasNext()) {
> Map.Entry mentry = (Map.Entry)iterator.next(); <> is this?
> System.out.print("key is: "+ mentry.getKey() + " & Value is:
> "); <> System.out.println(mentry.getValue());
> }
>
> }
> }
>
It's not a modern example of how to iterate over a TreeMap but I suspect
that it was also to give an example of how to use Map.Entry. If you
just want to print out the entries of the map in order you would use
something similar to this now.
import java.util.*;
public class test {
public static void main(String... args) {
TreeMap tmap = new TreeMap<>();
tmap.put(1,"Data1");
tmap.put(23,"Data2");
tmap.put(70,"Data3");
tmap.put(4,"Data4");
tmap.put(2,"Data5");
for (Integer key : tmap.keySet())
System.out.printf("key is: %d & value is: %s\n",
key,tmap.get(key));
}
}
C:\Users\Knute Johnson>java test
key is: 1 & value is: Data1
key is: 2 & value is: Data5
key is: 4 & value is: Data4
key is: 23 & value is: Data2
key is: 70 & value is: Data3
Keeping a SortedMap can be expensive and if you only occasionally need
it to be sorted you can sort the key set before you interrogate the Map.
import java.util.*;
public class test1 {
public static void main(String... args) {
Map tmap = new HashMap<>();
tmap.put(1,"Data1");
tmap.put(23,"Data2");
tmap.put(70,"Data3");
tmap.put(4,"Data4");
tmap.put(2,"Data5");
for (Integer key : new TreeSet(tmap.keySet()))
System.out.printf("key is: %d & value is: %s\n",
key,tmap.get(key));
}
}
C:\Users\Knute Johnson>java test1
key is: 1 & value is: Data1
key is: 2 & value is: Data5
key is: 4 & value is: Data4
key is: 23 & value is: Data2
key is: 70 & value is: Data3
--
Knute Johnson
_______________________________________________
hangout mailing list
hangout-at-nylxs.com
http://www.nylxs.com/
|
|
