Small Preconditions helper class for your Offensive Programming

Preconditions.java

import android.support.annotation.Nullable;

// Based on http://google-collections.googlecode.com/svn-history/r78/trunk/javadoc/com/google/common/base/Preconditions.html

public class Preconditions {

    public static void checkArgument(boolean expression, @Nullable Object errorMessage) {
        if (!expression) {
            throw new IllegalArgumentException(String.valueOf(errorMessage));
        }
    }

    public static void checkState(boolean expression, @Nullable Object errorMessage) {
        if (!expression) {
            throw new IllegalStateException(String.valueOf(errorMessage));
        }
    }

    public static <T> T checkNotNull(T reference, @Nullable Object errorMessage) {
        if (reference == null) {
            throw new NullPointerException(String.valueOf(errorMessage));
        }
        return reference;
    }

    public static <T> T checkNull(T reference, @Nullable Object errorMessage) {
        checkState(reference == null, errorMessage);
        return reference;
    }
}