Utilities

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package converter;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.StringTokenizer;

/**
 *
 * @author Acer
 */
public final class Utilities {
    private Utilities(){
    }

    @Checked
    public static boolean isDecimalDigit(char digit){
        return digit >= '0' && digit <= '9';
    }

    @Checked
    public static boolean isBinaryDigit(char digit){
        return digit == '0' || digit == '1';
    }

    @Checked
    public static boolean isOctalDigit(char digit){
        return digit >= '0' && digit <= '7';
    }

    @Checked
    public static boolean isHexadecimalDigit(char digit){
        return isDecimalDigit(digit) || ((digit >= 'a' && digit <= 'f') || (digit >= 'A' && digit <= 'F'));
    }

    @Checked
    public static int toDecimalValue(char hex){
        if(isDecimalDigit(hex))
            return Character.digit(hex, 10);
        switch(hex){
            case 'A':
            case 'a':
                return 10;
            case 'B':
            case 'b':
                return 11;
            case 'C':
            case 'c':
                return 12;
            case 'D':
            case 'd':
                return 13;
            case 'E':
            case 'e':
                return 14;
            case 'F':
            case 'f':
                return 15;
            default:
                return -1;
        }
    }

    @Checked
    public static char toHexadecimalDigit(int value){
        if(value >= 0 && value <= 9)
            return Character.forDigit(value, 10);
        switch(value){
            case 10:
                return 'A';
            case 11:
                return 'B';
            case 12:
                return 'C';
            case 13:
                return 'D';
            case 14:
                return 'E';
            case 15:
                return 'F';
            default:
                return '\0';
        }
    }

    @Checked
    public static String[] split(String str, int splitsCount, int charsCount){
        if(splitsCount <= 0 || charsCount <= 0)
            return new String[]{str};
        StringBuilder builder = new StringBuilder();
        int count = 0;
        for(int i = 0;i < str.length();i++){
            if((i % charsCount) == 0 && i != 0){
                builder.append("-");
                count++;
            }
            if(count == splitsCount){
                builder.append(str.substring(i));
                break;
            }
            builder.append(str.charAt(i));
        }
        StringTokenizer tokenizer = new StringTokenizer(builder.toString(), "-");
        ArrayList<String> groups = new ArrayList<>();
        while(tokenizer.hasMoreTokens())
            groups.add(tokenizer.nextToken());
        return groups.toArray(new String[]{});
    }

    @Checked
    public static String reverse(String str){
        String temp = "";
        for(int i = str.length()-1;i >= 0;i--)
            temp += str.charAt(i);
        return temp;
    }

    @Checked
    public static Iterator<Character> stringIterator(String str){
        Character[] data = new Character[str.length()];
        for(int i = 0;i < str.length();i++)
            data[i] = str.charAt(i);
        return Arrays.asList(data).iterator();
    }

    @Checked
    public static StringBuilder[] stringBuildersArrayFor(String[] array){
        StringBuilder[] builders = new StringBuilder[array.length];
        for(int i = 0;i < array.length;i++)
            builders[i] = new StringBuilder(array[i]);
        return builders;
    }
}