/*
 * Copyright 2019, TeamDev. All rights reserved.
 *
 * Redistribution and use in source and/or binary forms, with or without
 * modification, must retain the above copyright notice and the following
 * disclaimer.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package io.spine.tools.compiler.validation;

import static com.google.common.base.Preconditions.checkNotNull;
import static java.lang.String.format;

/**
 * Utility class for working with method code generation.
 */
final class Methods {

    /** Prevents instantiation of this utility class. */
    private Methods() {
    }

    /** Returns the `return` statement for the methods of the `ValidatingBuilder` classes.*/
    static String returnThis() {
        return returnValue("this");
    }

    static String returnValue(String value) {
        return "return " + value;
    }

    static String callMethod(String receiver, String methodName, String... parameters) {
        checkNotNull(receiver);
        checkNotNull(methodName);
        checkNotNull(parameters);
        StringBuilder superMethodCall = new StringBuilder();
        superMethodCall.append(format("%s.%s(", receiver, methodName));
        String parameterList = String.join(", ", parameters);
        superMethodCall.append(parameterList).append(')');
        return superMethodCall.toString();
    }

    /** Returns a call to the specified method of the parent class with the specified parameters. */
    static String callSuper(String methodName, String... parameters) {
        return callMethod("super", methodName, parameters);
    }

    /** Returns the getter code fragment of the predefined {@code Message.Builder}. */
    static String getMessageBuilder() {
        return "getMessageBuilder()";
    }
}

@@ -1544,24 +1544,53 @@
 ng value) %7B%0A
+        checkNotNull(value);%0A
         retu

Add a null check.