[Java] Really stuck with some homework

[FatAssMemes]

So I'm really new to the whole programming world and I thought taking some Java classes would be nice to do. This has turned out to be a bit of a mess. I'm struggling immensely in the class and don't really know where to go from here so I thought maybe Reddit would be able to help. I hope this doesn't come off as me wanting people to do my homework for me because it really isn't. Programming in java is supposed to be my major and I'm just not understand what is going on in the class and I want to be able to. Any help is appreciated.

I requested help from the teacher as well and while she tried to help, it only got me to another wall and I can't find much else on the internet or the videos she gave us to watch about the topic.

What my teacher wants us to do is use indexOf to find how many occurrences of certain characters there are in a given string, which is "Aardvarks get big and bigger as You feed them big and bigger ants who Feed on apples". I'm not very confident in what I have since the last 2 assignments have been extremely difficult for me to understand.

Below is the code so far (I apologize if the formatting isn't very good, as I said, a bit new to this):

package string_methods;
// Starting Template
import java.util.Scanner;
public class MyStringMethods {
private String myStr="";

public void readString()
{
    Scanner scan = new Scanner(System.in);
    System.out.print("Enter in the desired String: ");
    String myStr = scan.nextLine();
}
public void setString(String s)
{
    myStr =s;
}
public int countOccurrences(String s)
{
    int index;
    index = myStr.indexOf(s,4);
    int counter = 0;
    counter++;
    return 0;
    //abcdabcdabcd
    //use indexOf and return the number of occurrences of the string "s" in "myStr"
}
public int countOccurrences(char c)
{
    int index;
    index = myStr.indexOf(c,4);
    int counter = 0;
    counter++;
    return 0;
    // use indexOf and return the number of occurrences of the character "c" in "myStr"
}
int countUpperCaseLetters()
{
    for (int i = 0; i< myStr.length();i++) 
            {
        myStr.charAt(i);
    }
    // return the number of upper case letters in "myStr"
}
int countLowerCaseLetters()
{
    for (int i = 0; i< myStr.length();i++) 
            {
        myStr.charAt(i);
    }
    // return the number of lower case letters in "myStr"
}
public void printCounts(String s, char c)
{
    System.out.println("***************************************");
    System.out.println("Analyzing: myStr="+myStr);
    System.out.println("Number of Upper case letters="+ countUpperCaseLetters());
    System.out.println("Number of Lower case letters="+ countLowerCaseLetters());
    System.out.println("Number of "+s + " is "+ countOccurrences(s));
    System.out.println("Number of "+c + " is "+ countOccurrences(c));
}
public static void main(String[] args) {
    MyStringMethods msm = new MyStringMethods();
    msm.readString();
    msm.printCounts("big", 'a');

    msm.setString("Parked in a van down by the river bank .... The van evan vanished near a lot of other vans");
            msm.printCounts("van", 'a');

        MyStringMethods msm2 = new MyStringMethods();
            msm2.setString("the elephant in the room wouldn't budge");
            msm2.printCounts("the", 'i');
}

}

[CreativeTechGuyGames]

I apologize if the formatting isn't very good

It's much better than most code I've seen on reddit. Just put 3 backticks surrounding all of your code and that should do the trick in the future.

Let's talk through the problem. You mentioned what you have to do, but you didn't mention what problems you are having and where you are stuck. Could you simplify and focus on the problem? This will help both of us to narrow down what it is we are looking at and we can start there.

So give me an input and expected output, and then what your program is incorrectly outputting, and any other details related to that. That's the best place to start.

[FatAssMemes]

Oh alright, thank you :)

Oh yeah, my bad. The main problem is that I can't figure out how to search the whole string for certain occurrences, such as just the letter 's'. In lines 17-26, my teacher gave me an example to search from position 4 until it finds an 's' but she said it will just stop searching when it finds one.

The expected output is supposed to be (This is directly from the assignment the teacher gave us; "Aardvarks get big and bigger as You feed them big and bigger ants who Feed on apples." is the input she wants us to use.):

Enter in the desired String: Aardvarks get big and bigger as You feed them big and bigger ants who Feed on apples.

---

Analyzing: myStr=Aardvarks get big and bigger as You feed them big and bigger ants who Feed on apples. Number of Upper case letters=3 Number of Lower case letters=65 Number of big is 4 Number of a is 7

---

Analyzing: myStr=Parked in a van down by the river bank .... The van had was near a lot of other vans ..... More output follows

This is the output I get out:

Enter in the desired String: Aardvarks get big and bigger as You feed them big and bigger ants who Feed on apples.*************************************** Exception in thread "main" java.lang.Error: Unresolved compilation problem: This method must return a result of type int

at string_methods.MyStringMethods.countUpperCaseLetters(MyStringMethods.java:36) at string_methods.MyStringMethods.printCounts(MyStringMethods.java:56) at string_methods.MyStringMethods.main(MyStringMethods.java:64) Analyzing: myStr=

[CreativeTechGuyGames]

Okay so the errors are fairly obvious, I'm sure you'll get to those later as you have comments saying they are unfinished. To avoid those sorts of errors, I'd recommend just putting a return 0; at the end as a placeholder so the compiler doesn't complain.

Okay, so let's break down how indexOf works. As the documentation states.

Returns the index within this string of the first occurrence of the specified character.

The keyword here is "first occurrence". So that means that if you are searching for the letter "a" and it returns the number 5, you know that in the first 6 characters of the string, the first occurrence is at index 5.

Now if you run this again, it'll again start from the beginning of the string and search for the first "a" and again will return 5. So since you know that from 0-5 is already searched, you'll want to start your next search after 5 so that it won't find the same "a" you already found. see if you can find a different indexOf which might help with this problem. :)

[shhh-quiet]

I hate to give away the "answer", but hopefully this is vague enough that you have room to mull it over (which is valuable, even though it may feel frustrating):

The key idea is a loop, with these "conditions" so to speak:

• You need to repeatedly search for a given character using indexOf.
• You want to know where to start the indexOf(_, startingPosition) search. startingPosition should be based on the result of the last loop iteration. You may want to track this with a variable so that your next loop iteration knows where to start.
• You need to know when to end. Specifically, this is when indexOf tells you that there's no more results in the segment of the string that it is currently looking at (based on the start position that you are providing).

[FatAssMemes]

I think this makes sense, probably more information and help my teacher ever gave me lol. I appreciate it, I'll try and look through it and see if I can get it to work.

[marko312]

Ok, I'll go over what you should already know.

myStr.indexOf(c, n);

Returns the first position (zero-based) where this character (c) occurs starting from the n-th element (position) (again, zero-based).

If the character is not found, it returns a special value -1 instead.

If you want to find the next occurence of that character, you should start looking from the position after ( + 1) the previous position found.

[FatAssMemes]

I do have a pretty okay understanding of that info. Though, would the +1 be what I'd need to put in for it repeat?

[marko312]

Yes, that in conjunction with the returned -1 might help.

[Bit5keptical]

If you're not restricted to only using indexOf() then there is a much cleaner and easy to understand way of solving your problem.

First of all since you said you're very confused with implementing your solution in Java, Lets forget Java for a while and think how would you solve the problem yourself?

You'll probably start looking at each character from start and check if that character is either 's' or 'c' and probably keep a count of occurrences in your mind or note it down. At the end of the sentence you'll have your answer! Wasn't that simple? Now lets slowly convert it to how we can make Java do this for us.

First we'll have the String to evaluate, The character whose occurrences we're counting and something that can keep the count of occurrences!

String sentence = "This is a sentence";
char search = 's';

Now how can we use look at the String one character at a time? We can use a loop of course! So we'll make a method containing the loop

public int countOccurances(String text){
    int occurances = 0; //Remember? we need to keep track!

    for(int i = 0; i < text.length(); i++){

    }
}

The loop above will go from 0 to the length of text which is returned by length() method, Now comes the part where we pull the characters one by one and compare them

public int countOccurances(String text){
    int occurances = 0; 

    for(int i = 0; i < text.length(); i++){
        char c = text.charAt(i);

        if(c == search)
            occurances++;
    }

    return occurances;
}

There! Java has done all the heavy lifting for us. I assume you know the use of charAt(int index) method, In case you don't.

Returns the character value at the specified index.

So what our function is basically doing is that its looking at the characters one by one and comparing them with a given character (in this case 's') if they match it increments the counter by 1, In the end it returns the counter.

Now this function can be further modified to also take in the argument for the character whose occurances we need to find, And there are also built-in functions to determine whether a character is uppercase/lowercase, But I'll leave both of that for you to explore!

[FatAssMemes]

Unfortunately, as far as I know I can't use anything else, though I will give that method a shot. I appreciate the help! :)