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Thread: Help with Character arrays

  1. #1
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    Default Help with Character arrays

    Deleted for privacy.
    Last edited by shanklove; September 7th, 2010 at 05:57 PM.


  2. #2
    Super Moderator helloworld922's Avatar
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    Default Re: Help with Character arrays

    Unfortunately, Java's auto-boxing and auto-unboxing feature has a few gaps in what's covered. If you change your array to a char array rather than a Character array it should work.

    public static String getDigits( char[] array ) {
            String str = new String(array);
            if (str == "") {
                return " ";
            }
            StringBuffer strBuff = new StringBuffer();
            char c;    
            for (int i = 0; i < str.length() ; i++) {
                c = str.charAt(i);         
                if (Character.isDigit(c)) {
                    strBuff.append(c);
                }
            }
            return strBuff.toString();
        }
    }

    A better solution though is to simply straight up take a string rather than a char array which may or may not be filled.

    edit:
    fixed typo
    Last edited by helloworld922; September 6th, 2010 at 12:16 PM.

  3. #3
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    Default Re: Help with Character arrays

    Quote Originally Posted by helloworld922 View Post
    Unfortunately, Java's auto-boxing and auto-unboxing feature has a few gaps in what's covered. If you change your array to a char array rather than a Character array it should work.

    public static String getDigits( char[] array ) {
            char[] charArray = new char[] {array};
            String str = new String(charArray);
            if (str == "") {
                return " ";
            }
            StringBuffer strBuff = new StringBuffer();
            char c;    
            for (int i = 0; i < str.length() ; i++) {
                c = str.charAt(i);         
                if (Character.isDigit(c)) {
                    strBuff.append(c);
                }
            }
            return strBuff.toString();
        }
    }

    A better solution though is to simply straight up take a string rather than a char array which may or may not be filled.
    See I was going to do that, however, the test case that we were given has to be Character[]:
    	@Test
    	public void testGetDigitsWithListEmpty() {
    		Character[] values   = { };
    		Character[] actual   = Lab03One.getDigits( values );
    		Character[] expected = { };
     
    		assertArrayEquals( "The result is incorrect", expected, actual );
    	}
    	@Test
    	public void testGetDigitsWithListWithNoDigits() {
    		Character[] values = { 'y', 'o', 'd', 'a' };
    		Character[] actual = Lab03One.getDigits( values );
    		Character[] expected = { };
     
    		assertArrayEquals( "The result is incorrect", expected, actual );
    	}
    	@Test
    	public void testGetDigitsWithListWithLettersAndDigits() {
    		Character[] values = { 'C', '-', '3', 'P', 'O' };
    		Character[] actual = Lab03One.getDigits( values );
    		Character[] expected = { '3' };
     
    		assertArrayEquals( "The result is incorrect", expected, actual );
    	}
    	@Test
    	public void testGetDigitsWithListWithDuplicatedDigits() {
    		Character[] values = { 'a', '3', '2', 'b', '1', '2', 'c', '3', 'd' };
    		Character[] actual = Lab03One.getDigits( values );
    		Character[] expected = { '3', '2', '1', '2', '3' };
     
    		assertArrayEquals( "The result is incorrect", expected, actual );
    	}

  4. #4
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    Default Re: Help with Character arrays

    Quote Originally Posted by helloworld922 View Post
    Unfortunately, Java's auto-boxing and auto-unboxing feature has a few gaps in what's covered. If you change your array to a char array rather than a Character array it should work.

    char[] charArray = new char[] {array};
    That won't compile, you're assigning a char[] to char.
    Last edited by eyp; September 6th, 2010 at 08:39 AM.
    Eduardo Yez Parareda
    http://serfj.sourceforge.net - Simple Ever REST Framework for Java
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    Default Re: Help with Character arrays

    Quote Originally Posted by shanklove View Post
    My thought is that I need to take the array and make it into a String. Then take the string and take out everything that isn't a digit. Then return that String. But like I said, it's not working. Eclipse is throwing me the error:

    Character[] charArray = new Character[] {array};
    "Cannot convert from Character[] to Character

    and
    String str = new String(charArray);
    "The constructor String(Character[]) is undefined".
    You can do something like this... I think you don't need any String either a char[].

        public static String getDigits( Character[] array ) {
            if (array.length == 0) {
                return " ";
            }
            StringBuffer strBuff = new StringBuffer();
            char c;     
            for (int i = 0; i < array.length ; i++) {
                if (Character.isDigit(array[i])) {
                    strBuff.append(array[i]);
                }
            }
            return strBuff.toString();
        }
    Eduardo Yez Parareda
    http://serfj.sourceforge.net - Simple Ever REST Framework for Java
    http://serfj.wordpress.com

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    Super Moderator helloworld922's Avatar
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    Default Re: Help with Character arrays

    Quote Originally Posted by eyp View Post
    That won't compile, you're assigning a char[] to char.
    oops, my bad. I accidentally mixed several thoughts together (yay for late nights)

  7. #7
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    Default Re: Help with Character arrays

    Quote Originally Posted by eyp View Post
    You can do something like this... I think you don't need any String either a char[].

        public static String getDigits( Character[] array ) {
            if (array.length == 0) {
                return " ";
            }
            StringBuffer strBuff = new StringBuffer();
            char c;     
            for (int i = 0; i < array.length ; i++) {
                if (Character.isDigit(array[i])) {
                    strBuff.append(array[i]);
                }
            }
            return strBuff.toString();
        }
    Looks good in theory, but it fails all of these tests:
    It has something to do with "Lab03One.getDigits( values )"
    Cannot convert from String to Character[].

    Here is the whole test code, ignore the part about getMedian, all that works and compiled.

    import static org.junit.Assert.*;
     
    import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.List;
     
    import org.junit.Test;
     
    public class Lab03OneTest {
     
    	@Test
    	public void testGetMedianWithEmptyList() {
    		Integer[] values   = { };
    		Double    actual   = Lab03One.getMedian( values );
    		Double    expected = 0.0;
     
    		assertEquals( "The result is incorrect", expected, actual );
    	}
    	@Test
    	public void testGetMedianWithListOneValue() {
    		Integer[] values   = { 5 };
    		Double    actual   = Lab03One.getMedian( values );
    		Double    expected = 5.0;
     
    		assertEquals( "The result is incorrect", expected, actual );
    	}
    	@Test
    	public void testGetMedianWithListEvenValues() {
    		Integer[] values   = { 22, 19, 20, 21 };
    		Double    actual   = Lab03One.getMedian( values );
    		Double    expected = 20.5;
     
    		assertEquals( "The result is incorrect", expected, actual );
    	}
    	@Test
    	public void testGetMedianWithListOddValues() {
    		Integer[] values   = { 42, -27, 8, -2, 59, 42, -1 };
    		Double    actual   = Lab03One.getMedian( values );
    		Double    expected = 8.0;
     
    		assertEquals( "The result is incorrect", expected, actual );
    	}
     
    	@Test
    	public void testGetDigitsWithListEmpty() {
    		Character[] values   = { };
    		Character[] actual   = Lab03One.getDigits( values );
    		Character[] expected = { };
     
    		assertArrayEquals( "The result is incorrect", expected, actual );
    	}
    	@Test
    	public void testGetDigitsWithListWithNoDigits() {
    		Character[] values = { 'y', 'o', 'd', 'a' };
    		Character[] actual = Lab03One.getDigits( values );
    		Character[] expected = { };
     
    		assertArrayEquals( "The result is incorrect", expected, actual );
    	}
    	@Test
    	public void testGetDigitsWithListWithLettersAndDigits() {
    		Character[] values = { 'C', '-', '3', 'P', 'O' };
    		Character[] actual = Lab03One.getDigits( values );
    		Character[] expected = { '3' };
     
    		assertArrayEquals( "The result is incorrect", expected, actual );
    	}
    	@Test
    	public void testGetDigitsWithListWithDuplicatedDigits() {
    		Character[] values = { 'a', '3', '2', 'b', '1', '2', 'c', '3', 'd' };
    		Character[] actual = Lab03One.getDigits( values );
    		Character[] expected = { '3', '2', '1', '2', '3' };
     
    		assertArrayEquals( "The result is incorrect", expected, actual );
    	}
     
    }

    Not a clue where to go from here =\
    Also, I took out "char c" in the code you suggested (it was unused code)
    Last edited by shanklove; September 6th, 2010 at 02:02 PM.

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