String Arrays and how to loop them

Question

I was wondering if it is possible to make a loop for an array of strings that i want to evaluate in my code. I want to do more than one binary number at a time. So far I have this working correctly, however I cant figure our how to make it evaluate more than one binary number at a time. Thank you.

 package twoComplement;

public class bintodec {

public static void main (String[] args)throws java.io.IOException {

int number,
    digit1,
    digit2,
    digit3,
    digit4,
    digit5,
    digit6,
    digit7,
    digit8,
    result;

String num = "11100111";

number = Integer.parseInt(num);

digit1 = ((number % 100000000) - (number % 10000000 % 10000000)) / 10000000;
digit2 = ((number % 10000000) - (number % 10000000 % 1000000)) / 1000000;
digit3 = ((number % 1000000) - (number % 1000000 % 100000)) / 100000;
digit4 = ((number % 100000) - (number % 100000 % 10000)) / 10000;
digit5 = ((number % 10000) - (number % 10000 % 1000)) / 1000;
digit6 = ((number % 1000) - (number % 1000 % 100)) / 100;
digit7 = ((number % 100) - (number % 100 % 10)) / 10;
digit8 = (number % 10);

result = (digit1 * -128) + (digit2 * 64) + (digit3 * 32) + (digit4 * 16) + (digit5 * 8) + (digit6 * 4) + (digit7 * 2) + (digit8 * 1);

System.out.println ( "Binary number: " + num + "\nDecimal Number: " + result);
System.out.println();
System.exit( 0 );

}
}

bbedward · Accepted Answer · 2012-03-13 16:44:52Z

4

Yes, this is the purpose of loops ;-) An advanced for loop is the best way to iterate through an array. You can also iterate through collections (IE: ArrayList), which makes it easier to add new items.

String[] numbersToEvaluate = new String[]{"11100111", "100101", "10101101"};

for (String num: numbersToEvaluate)
{
    number = Integer.parseInt(num);

    digit1 = ((number % 100000000) - (number % 10000000 % 10000000)) / 10000000;
    digit2 = ((number % 10000000) - (number % 10000000 % 1000000)) / 1000000;
    digit3 = ((number % 1000000) - (number % 1000000 % 100000)) / 100000;
    digit4 = ((number % 100000) - (number % 100000 % 10000)) / 10000;
    digit5 = ((number % 10000) - (number % 10000 % 1000)) / 1000;
    digit6 = ((number % 1000) - (number % 1000 % 100)) / 100;
    digit7 = ((number % 100) - (number % 100 % 10)) / 10;
    digit8 = (number % 10);

    result = (digit1 * -128) + (digit2 * 64) + (digit3 * 32) + (digit4 * 16) + (digit5 * 8) + (digit6 * 4) + (digit7 * 2) + (digit8 * 1);

    System.out.println ( "Binary number: " + num + "\nDecimal Number: " + result);
}

answered Mar 13, 2012 at 16:44

bbedward

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1 Comment

Eric Goncalves Over a year ago

Worked perfectly, Thank you very much. I will mark as the answer when possible.

AlexR · Accepted Answer · 2012-03-13 16:46:30Z

1

This is the way to define string array:

int n = 10;
String[] arr = new String[n];

And here is how to iterate over array:

for (int i = 0; i < n; i++) {
    arr[i] = "element number " + i;
}

or this way:

for (String element : arr) {
    System.out.println(element);
}

answered Mar 13, 2012 at 16:46

AlexR

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Comments

Peter Lawrey · Accepted Answer · 2012-03-13 17:32:37Z

1

Do you mean something like

for (String num : "11100111,1010,11111,110101010101010101011101010101010101010101".split(",")) {
    long result = Long.parseLong(num, 2);
    System.out.println("Binary number: " + num + ", Decimal Number: " + result);
}

prints

Binary number: 11100111, Decimal Number: 231
Binary number: 1010, Decimal Number: 10
Binary number: 11111, Decimal Number: 31
Binary number: 110101010101010101011101010101010101010101, Decimal Number: 3665040856405

edited Mar 13, 2012 at 17:32

answered Mar 13, 2012 at 16:48

Peter Lawrey

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2 Comments

ggrigery Over a year ago

The built-in Integer.parseInt() conversion is nearly cheating :)

Peter Lawrey Over a year ago

@ggrigery It shouldn't be a problem unless this is [homework] ;)

Alex Wolf · Accepted Answer · 2015-02-25 14:08:49Z

1

If you are running at least Java 5, you can use a for-each construct to loop over any arbitrary Array or Collection.

String[] nums = //init
for (String num:nums) {
    // Do work.
}

If, however, you are on Java 1.4 or earlier, or you care about the index of the array, you need to use a traditional for loop

String[] nums = //init
for (int i = 0; i<nums.length; i++) {
    String num = nums[i];
    // Do work.
}

edited Feb 25, 2015 at 14:08

Alex Wolf

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answered Mar 13, 2012 at 16:47

Charlie

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Comments

Dunes · Accepted Answer · 2012-03-13 17:02:01Z

0

Yep, that's pretty easy.

String[] array = {"first", "second", "third"};
for (String element : array) {
   // do whatever
}

As an aside, however, you may wish to consider the following for clearer code.

String num = "1000";
int digit1 = Character.digit(num.charAt(0), 2);
// if you are only expecting a binary number then the second argument (2)
// tells the digit method to throw an error if it gets a digit other than 0 or 1
...

If this is for a school exercise or similar you may wish to test your code against the builtin Integer parser.

int numFromBinaryString = Integer.parseInt(numberString, 2);
// again, here the second argument tells parseInt to interpret numberString as
// binary string

answered Mar 13, 2012 at 17:02

Dunes

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