递归检查一个字符串是否等于另一个字符串

Question

my current code returns the output:

true
Expected: true

false
Expected: true

false
Expected: true

false
Expected: false

false
Expected: false 

So there's an issue with my logic that i'm not seeing

public static void main(String[] args)
{

    System.out.println(find("",""));
    System.out.println("Expected: true\n");

    System.out.println(find("Mitten","Mit"));
    System.out.println("Expected: true\n");
    System.out.println(find("I love my CS courses!"," CS"));
    System.out.println("Expected: true\n");
    System.out.println(find("","Cookies."));
    System.out.println("Expected: false\n");
    System.out.println(find("Java","Python"));
    System.out.println("Expected: false\n");


}
public static boolean find(String text, String str)
{

    boolean found = false;
    if(text.length() == 0 && str.length() == 0)
    {
        found = true;
        return found; 
    }
    if(text.length() == 0 || str.length() == 0)
    {
        return found; 
    }
    if(str.length() > text.length())
    {
        return found;
    }
    if(str.equals(text.substring(0,str.length()-1))) 
    {
        found = true;   
    }
    else
    {
        text = text.substring(1);
        find(text, str);
    }
    return found;
}

please help

Answer 1

I see an issue with this statement

if(str.equals(text.substring(0,str.length()-1))) 

Since the second index of substring is exclusive, it should be

if(str.equals(text.substring(0,str.length()))) 

in order to compare str to the first str.length characters of text .

Of course you can use text.contains(str) or text.startsWith(str) and eliminate some of your code, but perhaps that's not part of the exercise requirements.

Beside that issue, when you make a recursive call, you should usually do something with the value returned by that call :

found = find(text, str);

otherwise, why make the recursive call in the first place? (unless it has side effects of mutating the objects passed as parameters to the recursive call, which it does not in your case)