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Check if List / ArrayList contains Java string characters

I want to check if a string is found in the specified list filled with letters. For example, if I have:

ArrayList<String> list = new ArrayList();
list.add("a");
list.add("e");
list.add("i");
list.add("o");
list.add("u");

String str = "aeo";

for (int i = 0; i < list.size(); i++)
    for (int j = 0; j < str.length(); j++) {
        if (list.get(i).equals(str.charAt(j)))
            count++;
    }
System.out.println(count);

str is found in my list of letters, so I should see that my score is 3 because I found 3 matches for a string in my list. Anyway, the counter is printed with a value of 0. The basic idea is that I have to check if str is found in the list, regardless of the order of the letters in str.

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5 answers


You are comparing String

with Character

, so it equals

returns false

.

Compare char

instead:

for (int i = 0; i < list.size(); i++) {
    for (int j=0; j < str.length(); j++) {
        if (list.get(i).charAt(0) == str.charAt(j)) {
            count++;
        }
    }
}


Yours list

is supposed to contain only one String

s character . BTW, if this happens, you replace it with char[]

:

char[] list = {'a','e','i','o','u'};
for (int i = 0; i < list.length; i++) {
    for (int j = 0; j < str.length(); j++) {
        if (list[i] == str.charAt(j)) {
            count++;
        }
    }
}
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The string is not equal to the character, so you need to convert the character to string.

if (list.get(i).equals(String.valueOf(str.charAt(j))))


or a string to char and compare it like this:

if (list.get(i).getCharAt(0)==str.charAt(j))
+1


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You can use streams

to get the answer in one line like below with inline comments:

ArrayList<String> list = new ArrayList();
//add elements to list

String str = "aeo";//input string

//split str input string with delimiter "" & convert to stream
long count = Arrays.stream(str.split("")).//splt the string to array
    filter(s -> list.contains(s)).//filter out which one matches from list
    count();//count how many matches found
System.out.println(count);
+1


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Convert character to string:

list.get(i).equals(String.valueOf(str.charAt(j)))

The correct syntax for converting a character to a string is:

list.get(i).charAt(0) == str.charAt(j)

list.get(i).getCharAt(0)==str.charAt(j)

won't work as written in Jens' answer.

+1


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Yes, that's right. Thanks for this. And I just checked now and saw that I could make my list:

ArrayList<Character> list ;

instead

ArrayList<String> list ;
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