Method to check if a Char is present on a specific String

Question

I need to write a program where the main reads two strings as input: if the strings have the same length, then it has to pass the whole first string and the first char of the second string to a method called find, which has to return 'true' if the character appears even a single time on the string. If the length differs, then it will pass the whole second sentence and the last char of the first string to find. At last, the main will give whatever the method returns as output, so it has to be true, or false. I've created the whole main, and it works correctly, but I have no idea how to create the find method. Here is the code:

import java.util.Scanner;

public class Exercise {
    /*
     * public static boolean find(String... sentence, char... character) {
     *     // No, I can't use multiple varargs...
     * }
     */

    public static void main(String[] args) {
        String first, second;
        char firstChar, lastChar;
        Scanner keyboard = new Scanner(System.in);
        int lengthFirst, lengthSecond;
        boolean goal = true;

        first = keyboard.nextLine();
        lengthFirst = first.length();
        lastChar = first.charAt(lengthFirst - 1);

        second = keyboard.nextLine();
        lengthSecond = second.length();
        firstChar = second.charAt(0);

        System.out.println("Length 1: " + lengthFirst); // Those lines are test lines.
        System.out.println("Length 2: " + lengthSecond); // They're here just to check
        System.out.println("Char 1: " + firstChar); // if everything else works.
        System.out.println("Char 2: " + lastChar);

        if (lengthFirst == lengthSecond) {
            goal = find(first, firstChar);
            System.out.println("Goal is: " + goal);
            System.exit(0);
        } else
            goal = find(second, lastChar);
        System.out.println("Goal is: " + goal);
        System.exit(0);
    }
}

I was thinking about using the varargs option, using a varargs for the String, and another for the char, and then using a 'for' loop inside of the method to check if the character appears or not, and everything was easy on my head...but with some research I found out it will be a waste of time, because I can't use two varargs on the same method. The for loop idea works, but I can't figure out how to pass only the right String and the right Char. How should I pass them to the method, without passing them both?

Edit: No, this is not a duplicate. I allow loops, the other question doesn't. Also, my problem is about how am I supposed to pass multiple variables, but then using just some. That's an example:

The strings are both long 50, so the method needs to use only 'first' as String, and 'firstChar' as Char.

Answer 1

private static boolean find(String str, char Char) {
        for(int i=0;i<str.length();i++)
            if(str.charAt(i)==Char)
                return true;
        return false;
    }

This would help hopefully...

Answer 2

Find will simply contain

private boolean find(String subject, char first) {
    return subject.indexOf(first) > -1;
}

Answer 3

You can use String.indexOf().

returns the index within this string of the first occurrence of the specified character. If a character with value ch occurs in the character sequence represented by this String object, then the index (in Unicode code units) of the first such occurrence is returned, if no such character occurs in this string, then -1 is returned.

 public static boolean find(String str, char ch){
        if(str.indexOf(ch) == -1)
            return false;
        return true;
  } 

As you are thinking, you don't need four parameters for this function. You can use this function with two parameters for both cases:

  goal = find(first, firstChar);
  goal = find(second, lastChar);

EDIT I think you have misunderstood the way the parameters are mapped.

if you have a function like

      public static boolean find(String str, char ch){
              //do something
      }

You don't need to call the find with same parameters str and ch, I mean find(str,ch). You can call them with any parameter, with any name, like :

        goal = find(s,c); // s is a string and c is a char

        goal = find(a,b); // a is a string and b is a char

when you call find(s,c), s will be mapped to the first argument in your function that is str and c will be mapped to your second argument that is ch.

This is the reason you are able to call both find(first, firstChar) and find(second, lastChar) with a single function.

Answer 4

Seems like what you are looking for is:

if (second.indexOf(c) == -1) return false; //char c not found
return true;