Add first part of a persistent map implementation.

pdb-utils/src/main/java/org/lucares/utils/Preconditions.java

@@ -0,0 +1,32 @@
+package org.lucares.utils;
+
+import java.text.MessageFormat;
+import java.util.Objects;
+
+public class Preconditions {
+	public static void checkEven(final long value, final String message) {
+		if (value % 2 != 0) {
+			throw new IllegalStateException(message + ". Was: " + value);
+		}
+	}
+
+	/**
+	 *
+	 * @param a
+	 * @param b
+	 * @param message formatted with {@link MessageFormat}
+	 * @param args
+	 */
+	public static void checkGreater(final long a, final long b, final String message, final Object... args) {
+
+		if (a <= b) {
+			throw new IllegalStateException(MessageFormat.format(message, args) + " Expected: " + a + " > " + b);
+		}
+	}
+
+	public static void checkEqual(final Object actual, final Object expected) {
+		if (!Objects.equals(actual, expected)) {
+			throw new IllegalStateException();
+		}
+	}
+}