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Java Java Data Structures Organizing Data Arrays

Mozart Liessi
Mozart Liessi
2,618 Points
Posted by Mozart Liessi
Mozart Liessi
2,618 Points

I didn't understand when Graig wrote "String veggie: vegetables"

maybe it's a very simple question, but I didn't understand it yet

3 Answers

Dane Parchment
MOD
Dane Parchment
Treehouse Moderator 11,075 Points
Dane Parchment
Dane Parchment
Treehouse Moderator 11,075 Points

The colon is used in multiple places in Java, however, the most common place (in my opinion) is in the for-each loop.

Basically the for-each loop looks like this:

for(VariableType variableName: array|arrayList) {
//.......do stuff here
}

Basically what it is a loop that's sole purpose is to work for collections or lists like Array and ArrayList.

The syntax is saying: store each value indexed in the specified array or arrayList in the specified variable, then in the body of loop perform the specified action to that variable.

An example would be:

int [] list = [1, 2, 3, 4, 5, 6, 7, 8];

for(int number: list) {
System.out.println(number);
}

The output would be:

1
2
3
4
5
6
7
8

Hopefully that is enough information for you to understand how it works and what it does, if you still need help let me know.

EDIT: Remember that for the foreach loop to work the variable must be of the same type as the array, so if your array is a double then your variable should also be a double, and if it is a Dog object then your variable should also be a dog variable.

Mozart Liessi
Mozart Liessi
2,618 Points
Mozart Liessi
Mozart Liessi
2,618 Points

thanks very much, it got very clearly to me now

Sang Tran
Sang Tran
6,918 Points
Sang Tran
Sang Tran
6,918 Points

Hey Mozart, did you mean what Craig was doing at 3:32? He's creating a For each loop/ enhanced For loop. In that example, he wants to print out each veggie in his vegetables array. The variable name veggie can be called anything btw.

Example: for (String v : vegetables) { System.out.println(v); }

Aaron Arkie
Aaron Arkie
5,345 Points
Aaron Arkie
Aaron Arkie
5,345 Points

Hello Mozart, Craig is creating a "for-each" loop. This for-each loop is great when dealing with sifting through the elements of an array. The Syntax is as follows... 

for( datatype <variable-name> : <declared-array-variable>)
    {
        // do something extraordinary
    }

The datatype for the variable you are using to go into the array must match the elements found in the array. The best way to remember this loop is to say " For each time <variable-name> goes into my <array-variable>... do something.

You can achieve the same process using a normal for-loop

    for(int veggie = 0; veggie < vegetables.length; veggie++)
    {
       System.out.println(vegetables[veggie]);
    }

I hope this helps! This stackoverflow(http://stackoverflow.com/questions/85190/how-does-the-java-for-each-loop-work) might be of use to you.

EDIT: Changed to an answer instead of a comment - Dane E. Parchment Jr. (Moderator)