Rounding Double to 1 Decimal place

Hey guys, How would I round my Double to just 1 decimal e.g. from 1.552 to 1.5
Thx

 

TheGamesHawk2001
Try casting an int to it.

 

Creeoer int removes all decimals...

TheGamesHawk2001 use DecimalFormat

 

SuperOriginal
Misread his post

 

Saw that and wasn't that sure on how to implement it into my plugin.

Code:java

 @EventHandler
public void onChat(AsyncPlayerChatEvent event){
Player p = event.getPlayer();
 
if(chatCool.containsKey(p.getName())){
DecimalFormat df = new DecimalFormat("#.#");
double chatTime = chatCool.get(p.getName());
if(chatCool.get(p.getName()) > System.currentTimeMillis()){
event.setCancelled(true);
p.sendMessage(ChatColor.DARK_RED + "CANT TALK YET! talk in " + ((chatTime - System.currentTimeMillis())/1000) + " seconds!");

 

There's not much implementing to do.. Create DecimalFormat, then use DecimalFormal#format()

 

But in my instance, Where would I put it?, I have the "DecimalFormat decimalformat = new DecimalFormat("#.#");"
above the "double chatTime = chatCool.get(p.getName());" Where would I actually put it?

Here's all my code:

Code:java

    static HashMap<String, Long> chatCool = new HashMap<String, Long>();
 
    @EventHandler
    public void onChat(AsyncPlayerChatEvent event){
        Player p = event.getPlayer();
 
        if(chatCool.containsKey(p.getName())){
            DecimalFormat decimalformat = new DecimalFormat("#.#");
            double chatTime = chatCool.get(p.getName());
            if(chatCool.get(p.getName()) > System.currentTimeMillis()){
                event.setCancelled(true);
                p.sendMessage(ChatColor.DARK_RED + "" + ChatColor.BOLD + "FAULT" + ChatColor.GRAY + ": You can not talk yet. You will be able to talk in " + ((chatTime - System.currentTimeMillis())/1000) + " seconds!");
            } else {
                addCooldown(p, 1); //You can change the 10 to whatever you want the cooldown to be
            }
 
        } else {
            addCooldown(p, 1); //Same thing
        }
 
    }
 
    public void addCooldown(Player p, long secs){
        long currentMillis = System.currentTimeMillis();
        long coolTime = currentMillis + ((secs + 1) * 1000);
 
        chatCool.put(p.getName(), coolTime);
    }
}

 

TheGamesHawk2001 That's fine.. It doesn't matter where you put it, as long as you have access to it.

Now just wrap your math calculation in decimalformat.format()

 

TheGamesHawk2001
You would do that to replace line 12 :

Code:java

chatTime = Math.round((chatTime - System.currentTimeMillis()/1000) * 10) / 10;
p.sendMessage(ChatColor.DARK_RED + "" + ChatColor.BOLD + "FAULT" + ChatColor.GRAY + ": You can not talk yet. You will be able to talk in " + chatTime + " seconds!");

BTW:
If you round 1.552 to 1 decimal place, it doesn't make 1.5 but 1.6

 

TheGamesHawk2001 SuperOriginal A simpler solution could be : Math.floor(x * 10) / 10. The way this works is simple: you "shift" each digit up (1.52 becomes 15.2) and then round it, which gets rid of the other decimals (15.2 becomes 15). Finally you shift back the digits to their original position by dividing by 10 and that's it.

 

Totom3 Please enlighten me on how that is more simple.

 

Totom3 I ninja'd you, but Math.round is better because if it is 0.9 it will round it to 1, not 0
And SuperOriginal, it is more efficient and faster to do it that way...

 

Err...if all you do is to print the double value with one decimal you should use the String formatter:

Code:

String.format("My double is: %.1f", myDoubleValue);

 

au2001

I'd like to see the benchmarks that support your idea. Even if that is true, the difference is marginal enough to not matter. In any circumstance. Whatsoever.

In this case, readability triumphs, and the easiest answer to read is either SuperOriginal 's answer or Rocoty 's answer, both CLEARLY indicate exactly what they're trying to do without the need for comments, and do it in less lines.

Edit: wouldn't cause a floating point error, due to dividing by ten only changing the base, still not a good idea though.

 

Eh? No it won't. You're rounding to 1 decimal place - 0.9 is 1 decimal place, so it will just return 0.9... if it did return 1 (or 0 for that matter) then it'd be horribly wrong.

 

Easy one liner!

Code:java

 
double x = 12345.6789;
x = Double.parseDouble(Double.toString(x).substring(0, Double.toString(x).indexOf('.') + 2));
//x is now 12345.6
 

 

Jayke_ I think we have enough solutions for this now, don't you?

 

AdamQpzm There are never enough solutions to a problem.

 

Jayke_ I disagree - there'd be no real benefit to having hundreds of solutions posted to this little problem - there is a point at which someone is given too much choice, resulting in harder decisions. It's far easier to decide between 2 good things than 50 good things