get first and last element in ArrayList in Java

Question

I have small code where i have to add condition to get proper output.

if the element inside the mimeList is Last then go to else part. or to the if.

there is always 1 element in this ArrayList.

(if it has only one element then it means it is last element.)

for (int i = 0; i < mimeList.size(); i++) {
    StringBuffer sb = new StringBuffer();

    if () {
        queryString = sb.append(queryString).append(key)
        .append("=").append(mimeList.get(i)).append(" or ").toString();
    }else{
        queryString = sb.append(queryString).append(key)
        .append("=").append(mimeList.get(i)).toString();
    }
}

Pasting your homework? Move StringBuffer out of the loop. Get rid of that ugly redundancy. Check that there's a space between keys. What about the "or" between first and second list item? Good luck. — mgaert
– mgaert, Commented Aug 6, 2012 at 13:09

Priyank Doshi · Accepted Answer · 2012-08-06 13:21:03Z

11

Regarding the heading of your question:

get first and last element in ArrayList in Java

It should be pretty simple:

mimeList.get(0); // To get first
mimeList.get(mimeList.size()-1); //to get last

And regarding your if condition :

if(!(i==0 || i==mimeList.size()-1))

As you phrased it like:

if the element in mimeList is first or last it will go in else condition other wise in if condition

I used ! in if condition. Otherwise below is pretty cool:

if((i>0) && (i!=mimeList.size()-1))

edited Aug 6, 2012 at 13:21

answered Aug 6, 2012 at 13:09

Priyank Doshi

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Comments

Peter Lawrey · Accepted Answer · 2012-08-06 13:29:02Z

5

A simpler way to do with without lots of checks is to use seperator which is empty to start with.

StringBuilder sb = new StringBuilder();
String sep = "";
for (String s : mimeList) {
    sb.append(sep + key + "=" + s);
    sep = " or ";
}

answered Aug 6, 2012 at 13:29

Peter Lawrey

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2 Comments

GameBuilder Over a year ago

:I have edited my question. Plz chk and help. if the element inside the mimeList is Last then go to else part. or to the if.

Peter Lawrey Over a year ago

All you need is " or " between the key=value pairs. This is the simplest way to do that. You don't need an if and you don't need to repeat the code.

npinti · Accepted Answer · 2012-08-06 13:08:48Z

2

Something like so should work: if ((i > 0) && (i < mimeList.size() - 1)). Since in Java collections as 0 based, the first element will be at location 0 and the last will be at Collection.Size - 1, since accessing the Collection.Sizeth location will cause an out of bounds exception.

answered Aug 6, 2012 at 13:08

npinti

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Comments

Edd · Accepted Answer · 2012-08-06 14:26:08Z

2

From what I can gather from your question, you want something like the following:

ArrayList<Foo> foos = fooGenerator.generateFoos();

for(int i = 0; i < foos.size(); i++) {
    if(i != (foos.size() - 1)) {
        System.out.println("Front elements of ArrayList");
    }
    else {
        System.out.println("Last element of ArrayList!");
    }
}

edited Aug 6, 2012 at 14:26

answered Aug 6, 2012 at 13:12

Edd

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Comments

Mourad MAMASSI · Accepted Answer · 2016-12-19 16:29:41Z

2

ArrayList<int> foos = ArrayList<int>();

for the first is

foos.get(0);

for the last is

foos.get(foo.size - 1);

answered Dec 19, 2016 at 16:29

Mourad MAMASSI

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Comments

Kumar Vivek Mitra · Accepted Answer · 2012-08-06 13:10:09Z

1

Considering the i is Integer inside the ArrayList.

if ((i > 0) && (i < mimeList.size() - 1))

answered Aug 6, 2012 at 13:10

Kumar Vivek Mitra

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2 Comments

Anthony Grist Over a year ago

Technically i is an int (a primitive), not an Integer (an object).

GameBuilder Over a year ago

@KumarVivekMitra I have edited my question. Plz chk and help.

Boosty · Accepted Answer · 2012-08-06 13:09:02Z

0

You pretty much have the answer already in your code:

You loop from the first to the last element in your array.

first: having index 0, last: having index (size - 1)

This results in the following condition:

if ((i > 0) && (i < mimeList.size() - 1))

answered Aug 6, 2012 at 13:09

Boosty

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Comments

Logard · Accepted Answer · 2012-08-06 13:16:12Z

0

Try something like

if(i == 0 || i == mimeList.size() - 1)

Hope that helps!

edited Aug 6, 2012 at 13:16

answered Aug 6, 2012 at 13:08

Logard

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1 Comment

Logard Over a year ago

Yeah, was a bit to quick there. Edited answer.

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