Different character outputs using loops and strings

Question

I've just given this as a response to an absolute beginner on SO, and I'm wondering how terrible it is.

Output for an odd number of lines:

>
>>>
>>>>>
>>>
>

Output for an even number of lines:

>
>>>
>>>>>
>>>>>
>>>
> 

The code:

int lines = 7;
int half = lines/2;
String carat = ">";
int i;

//better to declare first or does it not matter?         

if(lines%2==0){boolean even = true;}
else{boolean even = false;}

for(i=1;i<=lines;i++){
        System.out.println(carat + "\n");
        if(i==half && even){System.out.println(carat+"\n");}
        if(((i>=half && even) || (i>=half+1)) && i!=lines){
                carat = carat.substring(0,carat.length()-2);
        }else{
                carat = carat + ">>";
        }
}

This code just seems so ugly, not considering the fact that there is no method that takes number of lines and that it is abusing integer rounding.

Answer 1

better to declare first or does it not matter?

No. These days most people believe variables should be declared as late as possible, right by where they are used.

This code just seems so ugly.

It is. A little whitespace in there would help a lot. Which is easier to read:

// This:
if(i==half && even){System.out.println(carat+"\n");}

// Or this:
if (i == half && even) {
  System.out.println(carat+"\n");
}

that it is abusing integer rounding.

There's no abuse, and it's not rounding. Truncation on integer arithmetic is a specified part of the language. Feel free to use it. In this case, it does exactly what you want.

If I were writing this, I'd do:

printCarats(int numLines) {    
  for (int line = 0; line < numLines; line++) {
    // Mirror vertically across center line.
    int halfLine = line;
    if (line > numLines / 2) halfLine = numLines - line - 1;

    int numCarats = 1 + halfLine * 2;
    for (int i = 0; i < numCarats; i++) {
      System.out.print(">");
    }
    System.out.println();
  }
}

Answer 2

    if(lines%2==0){boolean even = true;}     
    else{boolean even = false;} 

Does this work for you? First, it looks like this makes the even variable only have scope in the decision block. You shouldn't be able to reference this further down in the code if you are declaring it in the braces.

Also, you can probably get rid of the if/else by just using the logic test to define the even variable:

boolean even = (lines%2 == 0); //parens for clarity

Answer 3

Know your libraries, use your libraries...

int lines = 7;

for (int i = 0; i < lines; i++) {
    int k = Math.min(i, lines-i-1);
    char[] line = new char[2*k+1];
    java.util.Arrays.fill(line, '>');
    System.out.println(new String(line));
}

Answer 4

Since there are not any requirements listed for this simple program, except some output that is lacking detail and since this was given to a beginner, I would start with a template like the one included and start the new programmer off with good practices like, code indentation, comments use of CONSTANTS etc.

 /*
 * this program will print the > greater than sign when the loop index is even
 * and the < less than sign when the loop index is odd
 * the program will test up to the integer value 7
 * 
 * programmer name
 * date
 */

//begin class definition
public final class PrintStrings {

 //required main method
    public static void main(String[] args){
      String ODDCARAT = "<"; // ODDCARAT constant
      String EVENCARAT = ">";// EVENCARAT constant
      int i;
      //loop through 7
      for(i=1;i<=7;i++){
        //test if integer is odd or even by % by 2 and checking for remainder
        if(i %2 == 0){
            System.out.println(EVENCARAT);
        }else{
            System.out.println(ODDCARAT);
        }//end if
      }//end for
    }//end main

}//end class