/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
 
    // we want mostly 3 letters per key..... except PQRS
    // so, set the span for each letter to 1/3 of the full span, less a small
    // amount so that there can actually be 4 in some keys. 
    private static final double SPAN = (1.0 / 3.0) - (1.0 / 260.0);
    // and we want those 4 letters to happen on key 7 - 15 letters in.
    private static final double OFFSET = 7.0 - (SPAN * 15);
 
    public static final char charForKey(final char letter) {
        final int comp = Character.toUpperCase(letter) - 'A';
        if (comp < 0 || comp >= 26) {
            return letter;
        }
        char key = (char)('0' + OFFSET + comp * SPAN);
        // correct Z overflow to 10.
        return key > '9' ? '9' : key;
    }
 
    public static final String keysFromNumber(String input) {
        StringBuilder sb = new StringBuilder(input.length());
        input.chars().forEach(c -> sb.append(charForKey((char)c)));
        return sb.toString();
    }
 
    public static void main(String[] args) {
        for (int ch = ' '; ch < 125; ch++) {
            System.out.printf("Char '%s' > %s\n", (char)ch, charForKey((char)ch));
        }
        String[] inputs = {"1-800-Got-Junk", "Java Rocks!!!"};
        for (String input : inputs) {
            System.out.printf("%s -> %s\n", input, keysFromNumber(input));
        }
    }
 
}

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