add base to base int converter

inputOutputFlanagan/chosen_base_to_chosen_base.java

@@ -0,0 +1,59 @@
+import flanagan.io.KeyboardInput;
+import java.math.BigInteger;
+import java.lang.Math;
+import java.util.ArrayList;
+import java.util.List;
+
+public class chosen_base_to_chosen_base {
+
+    public static void main(String arg[]) {
+        KeyboardInput kb = new KeyboardInput();
+        String input_number = kb.readLine("input number =");
+        BigInteger input_base = kb.readBigInteger("input base =");
+        BigInteger output_base = kb.readBigInteger("output base =");
+
+        BigInteger current_number, decimal_number = BigInteger.ZERO;
+        String chartable = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+
+        /* exit when one of the chosen bases is too big for the chartable */
+        if (input_base.compareTo(BigInteger.valueOf(chartable.length())) == 1 ||
+            output_base.compareTo(BigInteger.valueOf(chartable.length())) == 1 ) {
+            System.out.println("Error: chosen base was out too big in " +
+                "respect to the chartable defined by this program");
+            System.exit(1);
+        }
+
+        /* calc decimal number */
+        for (int i = 0; i < input_number.length(); i++) {
+            current_number = BigInteger.valueOf(chartable.indexOf(
+                input_number.substring(i,i + 1)));
+            /* exit when digit is bigger than base allows */
+            if (input_base.compareTo(current_number) < 1 ) {
+                System.out.println("Error: Nonsensical input. Plase make sure " +
+                    "not to use digits bigger than the base allows");
+                System.exit(1);
+            }
+            decimal_number = decimal_number.add(current_number.multiply(
+                input_base.pow(input_number.length() - i - 1)));
+            
+        }
+
+        ArrayList<Character> remainders = new ArrayList<Character>();
+        String output_number = "";
+
+        /* calculate remainders */
+        while(decimal_number.compareTo(BigInteger.ZERO) > 0){
+            remainders.add(chartable.charAt(decimal_number.mod(output_base).intValue()));
+            decimal_number = decimal_number.divide(output_base);
+        }
+
+        /* reverse remainders to get the output number */
+        for (int i = 1;i <= remainders.size(); i++){
+            output_number += remainders.get(remainders.size()-i);
+        }
+
+        System.out.println(output_number);
+        System.out.printf("length: %d\n", output_number.length());
+        System.exit(0);
+    }
+}