Comparing 2 Strings with 1?

[Khoder Wassouf]

Hi

I'm trying to create this following Program:

Return true if the string "cat" and "dog" appear the same number of times in the given string.

catDog("catdog") → true
catDog("catcat") → false
catDog("1cat1cadodog") → true

..............................................................................................................................................

This is what I have been trying to do but it wont work!

package NormalStrings;

/*Return true if the string "cat" and "dog" appear the same number of times in the given string.

// catDog("catdog") -- true
// catDog("catcat") -- false
// catDog("1cat1cadodog") -- true

*/
public class Second {

	
	public void Check(String str)
	{
		
		String S1="dog";
		String S2="cat";
		
		int j=0;
		String x[] = {};
		String y[] = {};
		
	for(int i=0;i<S1.length() - str.length();i++)
	{
			
        if(str.regionMatches(i, S1, 0, S1.length()))
	    {
	    x[j+1]=str.substring(i,i + S1.length());
	
	    }
       
        if(str.regionMatches(i, S2, 0, S2.length()))
	    {
        	
	    x[j+1]=str.substring(i,i + S2.length());
	    
	    }
        
        
        
	}
    
	
	
		if(x[1]=="dog")
		{
			if(y[1]=="cat")
			{
				System.out.print("YES");
			}
		}
		else
	System.out.print("NO!");
	
		
		
		
		
		
	}
	public static void main(String[] args) {
		
	Second K=new Second();
	
	K.Check("dogcat");
		
	
		
		
		
			
	}

}

[Henry Wong]

   if(x[1]=="dog")  

Make sure you use the equals() method to compare strings. The "==" is used to compare references, and it is doubtful that the value returned from substring will be the same object as the one created for the string literal.

Henry

[Ankit Garg]

If you can, use regular expression to achieve this...

[Khoder Wassouf]

Henry Wong wrote:

   if(x[1]=="dog")  

Make sure you use the equals() method to compare strings. The "==" is used to compare references, and it is doubtful that the value returned from substring will be the same object as the one created for the string literal.

Henry

Why do you think that its doubtful that the value returned from substring will be the same object as the one created for the string literal???

[Khoder Wassouf]

Khoder Wassouf wrote:

Henry Wong wrote:

   if(x[1]=="dog")  

Make sure you use the equals() method to compare strings. The "==" is used to compare references, and it is doubtful that the value returned from substring will be the same object as the one created for the string literal.

Henry

Why do you think that its doubtful that the value returned from substring will be the same object as the one created for the string literal???

I did what you said but still same error!

if(x[1].equals(S1))
		{
			if(y[1].equals(S2))
			{
				System.out.print("YES");
			}
		}
		else
	System.out.print("NO!");

[Henry Wong]

Khoder Wassouf wrote:
I did what you said but still same error!

You do know that you never actually told us what this error that you encountered is, right?

Henry

[Henry Wong]

Ankit Garg wrote:If you can, use regular expression to achieve this...

Agreed. Implemented it in five minutes...

Henry

[Khoder Wassouf]

Henry Wong wrote:

Ankit Garg wrote:If you can, use regular expression to achieve this...

Agreed. Implemented it in five minutes...

Henry

It doesnt tell me what the error is..............it just compiles and then tells me there's an error on line......

But since you got it working with Regular expression....are you talking about the .matches one??
If you can also give me a copy of the code that worked with you

[Henry Wong]

Khoder Wassouf wrote:
It doesnt tell me what the error is..............it just compiles and then tells me there's an error on line......

It does tell you what the error is. You just need to know how to read it.

Anyway, just compiled and ran your program. It is an array out of bounds error -- basically, the array that you instantiated is not big enough for how you are using it. This is actually not surprising, since it looks like the array that you are creating are of size zero.

Henry

[Khoder Wassouf]

Henry Wong wrote:

Khoder Wassouf wrote:
It doesnt tell me what the error is..............it just compiles and then tells me there's an error on line......

It does tell you what the error is. You just need to know how to read it.

Anyway, just compiled and ran your program. It is an array out of bounds error -- basically, the array that you instantiated is not big enough for how you are using it. This is actually not surprising, since it looks like the array that you are creating are of size zero.

Henry

Hey Henry.........Mate I have only been programming in Java for 4 days now!.....getting ready for the SCJP exam which is in Mid January.
I have been programming in C# for 4 years but its been like a Year since I touched it

But anyway........This is what I got:

package NormalStrings;

/*Return true if the string "cat" and "dog" appear the same number of times in the given string.

// catDog("catdog") -- true
// catDog("catcat") -- false
// catDog("1cat1cadodog") -- true

*/
class Second {



	
	public void Check(String str)
	{
		
		String S1="dog";
		String S2="cat";
		
		int j=0;
		int l=0;
		String x[] = {};
		String y[] = {};
		
	for(int i=0;i<S1.length() - str.length();i++)
	{
			
        if(str.regionMatches(i, S1, 0, S1.length()))
	    {
	    x[j]=str.substring(i,i + S1.length());
	     j++;
	     
	    }
       
        if(str.regionMatches(i, S2, 0, S2.length()))
	    {
        	
	    x[l]=str.substring(i,i + S2.length());
	    l++;
	   
	    }
        
        
        
	}
    
	
	
		if(x[0].matches("dog"))
		{
			if(y[0].matches("cat"))
			{
				System.out.print("YES");
			}
		}
		else
	System.out.print("NO!");
	
		
		
		
		
		
	}
	public static void main(String[] args) {
		
	Second K=new Second();
	
	K.Check("dogcat");
		
	
		
		
		
			
	}

}

Help! .................Thanks

[Henry Wong]

Basically, you created an array of size zero at line 23. The for-loop starting at line 26 does absolutely nothing -- because the condition never succeeds. And then it dies at line 50, because you try to access the first element of the zero element array that you created at line 23.

Henry

[Khoder Wassouf]

Henry Wong wrote:
Basically, you created an array of size zero at line 23. The for-loop starting at line 26 does absolutely nothing -- because the condition never succeeds. And then it dies at line 50, because you try to access the first element of the zero element array that you created at line 23.

Henry

Ok Henry thanks.....it all makes sense now

So what Procedure would you advise me to use in order to compare the String's??..........I understand that you advised me to use the Regular expression.....Did that mean the .matches()???..............or what??

Thanks!

[Henry Wong]

Khoder Wassouf wrote:
just tell me where I should start looking at and what I should start trying!

I would recommend that you examine your code, and figure out why it is not following your design. In this case, why the condition is always failing. After all, you wrote all that code, why are you so easily willing to just dump it?

Now... not to be condescending -- it is just that newbies love to skip the design stage and jump immediately into code.... If you haven't figured out the algorithm yet, then I recommend that you stop; Take out a pen and paper, and figure out how to do it on paper first. You need to be able to do this yourself, on paper, before you are able to teach the computer how to do it. Just pretend you are the computer and work it out in very little steps. Once you do that, then you can convert the little steps into lines of code.

Henry

[Khoder Wassouf]

I see what you mean Henry and what your saying Its very true....... problem is Iv got the exam in mid January......So I was in a Hurry :P

Anyway thanks...... I re did the program and posted a new topic of a more meaningful question with a better code for this program!

Thanks again

[aadesh dongre]

Hi....


S1.length() - str.length()

I had Seen the above condition of for loop in check method..
But i m nt able to get it...
As you passing str String of length 6 char and S1 is of 3 it will give-3
but the condition look like false at first time....
Please elabrte about for loop condition

[Hrishikesh Yeshwant Alshi]

Henry,

I agree and appreciate the thought you guys have given while creating the rationales in JavaRanch forum.


Thanks,
-Hrishikesh

[Les Morgan]

i think i'd do something like this for my comparison logic:

    start=s.indexOf(t, start);
    while(start>-1){
      start++;
      start=s.indexOf(t, start);
      cnt++;
    }

to count the occurrences of each target

[Christoph Schreiber]

// developed for Java SE 8
boolean stringCheck(String s, String sub1, String sub2) {
	int counter1 = (s.length() - s.replace(sub1, "").length()) / sub1.length();
	int counter2 = (s.length() - s.replace(sub2, "").length()) / sub2.length();
	return counter1 == counter2;
}

This method will return true, if s contains sub1 and sub2 the same number of times. (sorry for my poor English)

At least one other solution doesn't work well in the following case: "I love my mamama and my dad very much.". If I search for "mama" and "dad", it will count "mama" two times and "dad" one time. My solution is working well.