Frog jumping code (AP comp science help!)

**CompScienceStudent1** · September 20th, 2011, 07:35 PM

My computer science teacher told my class to write a code where a frog jumps a staircase to eat a fly. The frog can only jump 3 stairs at once and the frog must jump any number of stairs input. The program must compute the number of possible ways the frog can get to the top of the staircase and also spit out the paths it can take. s= # of stairs
V My code so far has errors in the jumpsPossible method and I really don't understand why can anyone help?

class frog {
static int totalPaths=0;
	public static void jumpsPossible(int i, int s, String path){
		if (i==s){
			totalPaths++;
			System.out.println (path);
		}
		if (i<s){
			jumpsPossible(i+1,s,path+1);
			jumpsPossible(i+2,s,path+2);
			jumpsPossible(i+3,s,path+3);
		}
	}
	public static void main (String [] args) {
		Integer s = Integer.valueOf(args [0]);
		System.out.println ("Freddie the Frog will now jump" + s + " stairs to catch a fly!");
		jumpsPossible(0,s,"");
		System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");
	}
}

**Norm** · September 20th, 2011, 07:56 PM

Can you post the output from the program and add comments to show what it should be.

Please edit your post and wrap the code in code tags.
Press the Go Advanced button, select the code and press the #icon.

**CompScienceStudent1** · September 20th, 2011, 08:08 PM

the output should show (lets say the input is 5 stairs so. . .)
Freddie the Frog will now jump 5 stairs to catch a fly!
12345
1245
1345
1235
135
145
125
2345
245
235
25
345
35
Freddie can get to the top of the staircase in 13 ways.

**Norm** · September 20th, 2011, 08:12 PM

Is that the output from the program?
Can you copy the console for when you execute the program?
To copy the contents of the command prompt window:
Click on Icon in upper left corner
Select Edit
Select 'Select All' - The selection will show
Click in upper left again
Select Edit and click 'Copy'

Paste here.

**Norm** · September 20th, 2011, 08:12 PM

Please edit your post and wrap the code in code tags.
Press the Go Advanced button, select the code and press the #icon.

**CompScienceStudent1** · September 20th, 2011, 08:16 PM

No that is what should be the output
when i try to compile i get an error:
kulbir-sabharwals-imac:Raina kulbirsabharwal$ javac -classpath . frog.java
frog.java:18: cannot find symbol
symbol : variable jumpsPossible
location: class frog
System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");
^
1 error

**Norm** · September 20th, 2011, 08:18 PM

Where is the variable: jumpsPossible defined? The compiler can not find its definition.
You have a method by that name. Do you another variable with a new name?

**CompScienceStudent1** · September 20th, 2011, 08:29 PM

The method jumpsPossible is determining the number of possible combinations and the ways in which the frog can jump, so I am trying to print the results of that method in main. . .

**Norm** · September 20th, 2011, 10:02 PM

System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");

The above is coded as a variable, not a method. A method call ends with ()s like this:

jumpsPossible(0,s,"");

**CompScienceStudent1** · September 21st, 2011, 12:05 AM

but i wrote that o.o so confused x.x i did call the method

**Norm** · September 21st, 2011, 07:05 AM

System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");

Where do you define the variable (red) used in the above println statement?

**CompScienceStudent1** · September 21st, 2011, 03:04 PM

but its not a variable I'm trying to call the jumpsPossible method

**Norm** · September 21st, 2011, 03:18 PM

A method has () after it. Look at your code again. There are no ()s after the name in this statement:

System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible + " ways.");

Without ()s the compiler thinks its a variable. This is NOT a call to a method.

**CompScienceStudent1** · September 21st, 2011, 05:35 PM

so if i change jumpsPossible in that line to jumpsPossible (0,s,"")
this is the error:
frog.java:18: 'void' type not allowed here
System.out.println ("Freddie can get to the top of the staircase in " + jumpsPossible(0,s,"") + " ways.");

**Norm** · September 21st, 2011, 05:42 PM

: 'void' type not allowed here

That is because the jumpsPossible() method does NOT return any value. It is a void type.

Where is the number of jumps value stored? Do you have a class variable that has it?

Should the jumpsPossible() method return a value instead of being void?

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