Add elements to Array list

Question

I have an array list of array list:

ArrayList<ArrayList<Character>> NodesAndServices = new ArrayList<ArrayList<Character>>();

I want to add eachRow of NodesAndServices to another arraylist allChars:

    List<Character> allChars = new ArrayList<Character>();

    for (int i = 0; i < NodesAndServices.size(); i++) {
    List<Character> eachListRow = NodesAndServices.get(i);

    for (List<Character> chr : eachListRow) { //Error
        for (char ch : chr) {
            allChars.add(ch);
        }
    }
}

But u get compile time error:

required: java.util.list
found: java.lang.character

UPDATE

for (int i = 0; i < NodesAndServices.size(); i++) {
    List<Character> eachListRow = NodesAndServices.get(i);

    for (Character chr : eachListRow.get(i)) { //Error,foreach not applicable to type character

            allChars.add(each);
    }
}

Not related to the question, but NodesAndServices should start with a lowercase to meet Java conventions. — Joffrey
– Joffrey, Commented Aug 9, 2015 at 17:24

Joffrey · Accepted Answer · 2015-08-09 17:29:46Z

1

for (List<Character> chr : eachListRow) { //Error

When writing an enhanced for loop like this one, the loop variable chr will take the value of each element of the collection eachListRow, which is a List<Character>. Therefore, chr must be of type Character, not List<Character>.

Then you'll realize you don't even need the nested loop:

for (Character chr : eachListRow) { // OK
    allChars.add(ch);
}

Note: you could also use an enhanced for loop for the first loop, leading to the following code, which is much nicer to read:

List<Character> allChars = new ArrayList<Character>();

for (List<Character> eachListRow : NodesAndServices) {
    for (Character chr : eachListRow) {
        allChars.add(ch);
    }
}

answered Aug 9, 2015 at 17:29

Joffrey

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Comments

ka4eli · Accepted Answer · 2015-08-09 17:47:28Z

1

eachListRow is not a list of lists. Try this:

 for (Character chr : eachListRow) {...

Update:

 for (int i = 0; i < nodesAndServices.size(); i++) {
        List<Character> eachListRow = nodesAndServices.get(i);

        for (Character chr : eachListRow) {
            allChars.add(chr);
        }
    }

edited Aug 9, 2015 at 17:47

answered Aug 9, 2015 at 17:12

ka4eli

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2 Comments

Sajad Over a year ago

I get this error: foreach not applicable to type character

ka4eli Over a year ago

@S-H, remove this error line, it's redundant because you already got the character in chr. Just add chr to you result list.

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