Hexdump.java

public class Hexdump {
    public static void main(String[] args) {
        System.out.println("Hello");

        System.out.println(hexdump("Hello helo hell"));
    }
    
    public static String hexdump(String str) {
        char[] chars = str.toCharArray();
        StringBuilder sb = new StringBuilder();
        /*
         * ooooo  xx xx xx xx xx xx xx xx  |........|
         */
        for (int i = 0; i <= chars.length / 8; i++) {
            if (i * 8 >= chars.length) {
                break;
            }
            sb.append(String.format("%04x  ", i));
            for (int j = 0; j < 8; j++) {
                if (i * 8 + j >= chars.length) {
                    sb.append("   ");
                } else {
                    sb.append(String.format("%02x ", (int) chars[i * 8 + j]));
                }
            }
            sb.append(" |");
            for (int j = 0; j < 8; j++) {
                if (i * 8 + j >= chars.length) {
                    sb.append(" ");
                    continue;
                }
                int value = (int) chars[i * 8 + j];
                if (value >= 48 && value <= 57) {
                    sb.append(String.format("%c", chars[i * 8 + j]));
                } else if (value >= 65 && value <= 90) {
                    sb.append(String.format("%c", chars[i * 8 + j]));
                } else if (value >= 97 && value <= 122) {
                    sb.append(String.format("%c", chars[i * 8 + j]));
                } else {
                    sb.append(".");
                }
            }
            sb.append("|\n");
        }
        return sb.toString();
    }
}