Utility classes are written in Java for converting to binary, hex, octal and addition, subtraction using algorithms.

aprint.md

Example of using:

Please, write numbers: 
20161014 19970613
199706.13
Binary
Binary A:					Binary B:
01001100111010000111110110	01001100001011101000110101
Decimal A:					Decimal B:
20161014					19970613
Substract:					Decimal
000000000101110011111000001	190401

Hexadecimal
Hex A:			Hex B:
133A1F6			130BA35
Decimal A:		Decimal B:
20161014		19970613
Substract:		Decimal
002E7C1			190401

Octal
Oct A:			Oct B:
114720766		114135065
Decimal A:		Decimal B:
20161014		19970613
Substract:		Decimal
000563701		190401

Float to binary: 0110000110000011010.001000010100011110101110000101001

Binary.java

package converter;

/**
 * Class utility for converting numbers to binary and back
 * Addition and subtraction works for positive numbers
 * Converter works right. Converter use two's complement for negative numbers
 * <b>Functions:</b>
 * <ul>
 * <li>Converting integer to binary string</li>
 * <li>Converting floating point (double) to binary string</li>
 * <li>Addition binary string numbers</li>
 * <li>Subtraction binary string numbers</li>
 * </ul>
 *
 * @author tkaczenko
 * @see <a href="https://en.wikipedia.org/wiki/Two%27s_complement">https://en.wikipedia.org/wiki/Two%27s_complement</a>
 */
public class Binary {
    /**
     * Addition for binary string numbers
     *
     * @param s1 Binary string created with {@code Binary}
     * @param s2 Binary string created with {@code Binary}
     * @return Binary string as a result of addition
     */
    public static String addition(String s1, String s2) {
        if (s1 == null || s2 == null) return "";

        // Addition algorithm for binary numbers
        int first = s1.length() - 1;
        int second = s2.length() - 1;
        StringBuilder sb = new StringBuilder();
        int carry = 0;
        while (first >= 0 || second >= 0) {
            int sum = carry;
            if (first >= 0) {
                sum += s1.charAt(first) - '0';
                first--;
            }
            if (second >= 0) {
                sum += s2.charAt(second) - '0';
                second--;
            }
            carry = sum >> 1;
            sum = sum & 1;
            sb.append(sum == 0 ? '0' : '1');
        }
        if (carry > 0) {
            sb.append('1');
        }

        sb.reverse();

        /// FIXME: 15.10.16 Fix subtraction for positive and negative numbers using addition
        // Only for subtraction positive number
        if (s1.charAt(0) == '1' && s2.charAt(0) == '1') {
            sb.setCharAt(0, '1');
        } else {
            sb.setCharAt(0, '0');
        }

        return sb.toString();
    }

    /**
     * Subtraction for binary string numbers
     *
     * @param s1 Binary string created with {@code Binary}
     * @param s2 Binary string created with {@code Binary}
     * @return Binary string as a result of subtraction
     */
    public static String subtraction(String s1, String s2) {
        // Change sign of second number to use addition
        char c = (s2.charAt(0) == 1) ? '0' : '1';
        s2 = c + s2.substring(1);
        return addition(getTwosComplement(s1), getTwosComplement(s2));
    }

    public static String toBinary(double n) {
        String decimal = toBinary((int) n);
        double fraction = n - ((int) n);
        String val = decimal + ".";
        if (fraction < 0) {
            val += "0";
        }
        while (fraction > 0) {
            double r = fraction * 2;
            if (r >= 1) {
                val += "1";
                fraction = r - 1;
            } else {
                val += "0";
                fraction = r;
            }
        }
        return val;
    }

    public static String toBinary(int num) {
        StringBuilder stringBuilder = new StringBuilder();
        boolean isNegative = (num < 0);
        if (isNegative) {
            num = Math.abs(num);
        }
        while (num > 0) {
            stringBuilder.insert(0, num & 1);
            num >>= 1;
        }
        // If number < 7 add zero and next add sign cell
        for (int i = stringBuilder.length() - 1; i < 7; i++) {
            stringBuilder.insert(0, "0");
        }
        if (isNegative) {
            stringBuilder.insert(0, "1");
        } else {
            stringBuilder.insert(0, "0");
        }
        if (stringBuilder.length() == 0) {
            stringBuilder.append("0");
        }
        return stringBuilder.toString();
    }

    public static int toDecimal(String str) {
        double val = 0;
        int k = 1;
        if (str.charAt(0) == '1') {
            k = -1;
        }
        for (int i = 1; i < str.length(); i++) {
            if (str.charAt(i) == '1') {
                val += Math.pow(2, str.length() - 1 - i);
            }
        }
        val *= k;
        return (int) val;
    }

    /**
     * Get two's complement for binary negative number
     *
     * @param binaryInt Binary string created with {@code Binary}
     * @return String of two's complement
     */
    private static String getTwosComplement(String binaryInt) {
        if (binaryInt.charAt(0) == '1') {
            String invertedInt = invertDigits(binaryInt);
            return addition(invertedInt, "1");
        } else {
            return binaryInt;
        }
    }

    private static String invertDigits(String binaryInt) {
        StringBuilder stringBuilder = new StringBuilder(binaryInt);
        for (int i = 1; i < stringBuilder.length(); i++) {
            if (stringBuilder.charAt(i) == '1') {
                stringBuilder.setCharAt(i, '0');
            } else {
                stringBuilder.setCharAt(i, '1');
            }
        }
        return stringBuilder.toString();
    }
}

Hexadecimal.java

package converter;

/**
 * Class utility for converting numbers to hexadecimal and back
 * Addition and subtraction works, but I'm not sure that It works right always
 * Converter works right.
 * <b>Functions:</b>
 * <ul>
 * <li>Converting integer to hex string</li>
 * <li>Addition hex string numbers</li>
 * <li>Subtraction hex string numbers</li>
 * </ul>
 *
 * @author tkaczenko
 */
public class Hexadecimal {
    private static String digits = "0123456789ABCDEF";

    public static String addition(String s1, String s2) {
        if (s1 == null || s2 == null) return "";

        int first = s1.length() - 1;
        int second = s2.length() - 1;
        StringBuilder sb = new StringBuilder();
        int carry = 0;
        while (first >= 0 || second >= 0) {
            int sum = carry;
            if (first >= 0) {
                sum += digits.indexOf(s1.charAt(first));
                first--;
            }
            if (second >= 0) {
                sum += digits.indexOf(s2.charAt(second));
                second--;
            }
            carry = sum >> 4;
            sum = sum & 0x0F;
            sb.append(sum);
        }
        if (carry > 0)
            sb.append(carry & 0x0F);

        sb.reverse();
        return sb.toString();
    }

    public static String subtraction(String s1, String s2) {
        if (s1 == null || s2 == null) return "";

        int first = s1.length() - 1;
        int second = s2.length() - 1;
        StringBuilder sb = new StringBuilder();
        int carry = 0;
        while (first >= 0 || second >= 0) {
            int sub = carry;
            if (first >= 0) {
                sub += digits.indexOf(s1.charAt(first));
                first--;
            }
            if (second >= 0) {
                sub -= digits.indexOf(s2.charAt(second));
                second--;
            }
            carry = sub >> 4;
            sub = sub & 0x0F;
            sb.append(digits.charAt(sub));
        }
        if (carry > 0)
            sb.append(digits.charAt(carry & 0x0F));

        sb.reverse();
        return sb.toString();
    }

    public static String toHex(int num) {
        StringBuilder stringBuilder = new StringBuilder();
        while (num > 0) {
            int j = num & 0x0F;
            stringBuilder.insert(0, digits.charAt(j));
            num >>= 4;
        }
        return stringBuilder.toString();
    }

    public static int toDecimal(String str) {
        str = str.toUpperCase();
        double val = 0;
        for (int i = 0; i < str.length(); i++) {
            val += Math.pow(16, str.length() - 1 - i) * digits.indexOf(str.charAt(i));
        }
        return (int) val;
    }
}

Main.java

package com.company;

import converter.Binary;
import converter.Hexadecimal;
import converter.Octal;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        System.out.println("Please, write numbers: ");
        Scanner scanner = new Scanner(System.in);
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        double num = scanner.nextDouble();
        scanner.close();

        System.out.println("Binary");
        String binaryA = Binary.toBinary(a);
        String binaryB = Binary.toBinary(b);
        int decimalA = Binary.toDecimal(binaryA);
        int decimalB = Binary.toDecimal(binaryB);
        System.out.println("Binary A:\t\t\t\t\tBinary B:");
        System.out.println(binaryA + "\t" + binaryB);
        System.out.println("Decimal A:\t\t\t\t\tDecimal B:");
        System.out.println(decimalA + "\t\t\t\t\t" + decimalB);
        String res = Binary.subtraction(binaryA, binaryB);
        System.out.println("Substract:\t\t\t\t\tDecimal");
        System.out.println(res + "\t" + Binary.toDecimal(res));

        System.out.println("\nHexadecimal");
        String hexA = Hexadecimal.toHex(a);
        String hexB = Hexadecimal.toHex(b);
        int decA = Hexadecimal.toDecimal(hexA);
        int decB = Hexadecimal.toDecimal(hexB);
        System.out.println("Hex A:\t\t\tHex B:");
        System.out.println(hexA + "\t\t\t" + hexB);
        System.out.println("Decimal A:\t\tDecimal B:");
        System.out.println(decA + "\t\t" + decB);
        res = Hexadecimal.subtraction(hexA, hexB);
        System.out.println("Substract:\t\tDecimal");
        System.out.println(res + "\t\t\t" + Hexadecimal.toDecimal(res));

        System.out.println("\nOctal");
        String octA = Octal.toOctal(a);
        String octB = Octal.toOctal(b);
        int deA = Octal.toDecimal(octA);
        int deB = Octal.toDecimal(octB);
        System.out.println("Oct A:\t\t\tOct B:");
        System.out.println(octA + "\t\t" + octB);
        System.out.println("Decimal A:\t\tDecimal B:");
        System.out.println(deA + "\t\t" + deB);
        res = Octal.subtraction(octA, octB);
        System.out.println("Substract:\t\tDecimal");
        System.out.println(res + "\t\t" + Octal.toDecimal(res));

        System.out.println("\nFloat to binary: " + Binary.toBinary((num)));
        System.out.println();
    }
}

Octal.java

package converter;

/**
 * Class utility for converting numbers to octal and back
 * Addition and subtraction works, but I'm not sure that It works right always
 * Converter works right.
 * <b>Functions:</b>
 * <ul>
 * <li>Converting integer to octal string</li>
 * <li>Addition octal string numbers</li>
 * <li>Subtraction octal string numbers</li>
 * </ul>
 *
 * @author tkaczenko
 */
public class Octal {
    private static String digits = "01234567";

    public static String addition(String s1, String s2) {
        if (s1 == null || s2 == null) return "";

        int first = s1.length() - 1;
        int second = s2.length() - 1;
        StringBuilder sb = new StringBuilder();
        int carry = 0;
        while (first >= 0 || second >= 0) {
            int sum = carry;
            if (first >= 0) {
                sum += digits.indexOf(s1.charAt(first));
                first--;
            }
            if (second >= 0) {
                sum += digits.indexOf(s2.charAt(second));
                second--;
            }
            carry = sum >> 3;
            sum = sum & 0x07;
            sb.append(digits.charAt(sum));
        }
        if (carry > 0)
            sb.append(digits.charAt(carry & 0x07));

        sb.reverse();
        return sb.toString();
    }

    public static String subtraction(String s1, String s2) {
        if (s1 == null || s2 == null) return "";

        int first = s1.length() - 1;
        int second = s2.length() - 1;
        StringBuilder sb = new StringBuilder();
        int carry = 0;
        while (first >= 0 || second >= 0) {
            int sub = carry;
            if (first >= 0) {
                sub += digits.indexOf(s1.charAt(first));
                first--;
            }
            if (second >= 0) {
                sub -= digits.indexOf(s2.charAt(second));
                second--;
            }
            carry = sub >> 3;
            sub = sub & 0x07;
            sb.append(digits.charAt(sub));
        }
        if (carry > 0)
            sb.append(digits.charAt(carry & 0x07));

        sb.reverse();
        return sb.toString();
    }

    public static String toOctal(int num) {
        StringBuilder stringBuilder = new StringBuilder();
        while (num > 0) {
            int j = num & 0x07;
            stringBuilder.insert(0, digits.charAt(j));
            num >>= 3;
        }
        return stringBuilder.toString();
    }

    public static int toDecimal(String str) {
        double val = 0;
        for (int i = 0; i < str.length(); i++) {
            val += Math.pow(8, str.length() - 1 - i) * digits.indexOf(str.charAt(i));
        }
        return (int) val;
    }
}