javademos/kdf/src/Fx.java

import java.util.HexFormat;

/** Tiny helpers shared by the demos: hex, a self-checking assert that prints PASS/FAIL, section headers. */
final class Fx {
    private static final HexFormat HEX = HexFormat.of();
    static int failures = 0;

    static String hex(byte[] b) { return HEX.formatHex(b); }
    static byte[] unhex(String s) { return HEX.parseHex(s.replaceAll("\\s+", "")); }

    /** Bytes 0x00..n-1 starting at {@code from} (RFC 5869 test case 2 uses such ranges). */
    static byte[] range(int from, int count) {
        byte[] b = new byte[count];
        for (int i = 0; i < count; i++) b[i] = (byte) (from + i);
        return b;
    }

    static byte[] fill(int value, int count) {
        byte[] b = new byte[count];
        java.util.Arrays.fill(b, (byte) value);
        return b;
    }

    static void check(String what, boolean ok) {
        System.out.println((ok ? "PASS  " : "FAIL  ") + what);
        if (!ok) failures++;
    }

    static void checkEq(String what, byte[] expected, byte[] actual) {
        check(what, java.util.Arrays.equals(expected, actual));
        if (!java.util.Arrays.equals(expected, actual)) {
            System.out.println("      expected " + hex(expected));
            System.out.println("      actual   " + hex(actual));
        }
    }

    static void header(String s) { System.out.println("== " + s); }

    /** Exit non-zero if any check failed, so run.sh and CI notice. */
    static void done() {
        System.out.println(failures == 0 ? "ALL CHECKS PASSED" : failures + " CHECK(S) FAILED");
        if (failures != 0) System.exit(1);
    }
}