检查字符串是否有字符循环

Question

I need to validate user input string to make sure it contains a comma. If it does not contain a comma it must print "Error" and allow for the user to re-enter input. I'm just not sure which loop to use. If else may work, but I need it to loop back to the scanner for the user input. Or a while loop that uses .contains? Thanks.

Answer 1

If you want to use a loop, I recommend the for-each loop:

boolean found = false;
while (found == false) {
    String input = "this is a sentence, with a comma"; // read input here
    for (char ch: input.toCharArray()) {
        if (ch == ',')  {
            found = true;
        } 
    }
    if (found == false) {
        System.out.println("Error");
    }
}

there will probably be functions built-in in Java for this, like "string.contains(character)" returning a boolean value

input.contains(",")

Answer 2

for loop will be best for such situation. But you can solve this problem using any of your preferred loops.

Solution using for loop

lets say the string you get is in a variable string1

enterdata: //ask for user to enter the string here
        for(int i=0;i<string1.length();i++){
            char c = string1.charAt(i);
            if(",".equals(c))
                continue correct;

            }
                if(true) continue enterdata; //this is just like goto statement
        correct:

        //write your code here