io.fabric8.zjsonpatch.internal.guava.Preconditions Maven / Gradle / Ivy

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/**
 * Copyright 2016 flipkart.com zjsonpatch.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.fabric8.zjsonpatch.internal.guava;

// Borrowed from Guava to get rid of the transitive dependency - thanks!
public class Preconditions {

  /**
   * Ensures that an object reference passed as a parameter to the calling method is not null.
   *
   * @param reference            an object reference
   * @param errorMessageTemplate a template for the exception message should the check fail. The
   *                             message is formed by replacing each {@code %s} placeholder in the template with an
   *                             argument. These are matched by position - the first {@code %s} gets {@code
   *                             errorMessageArgs[0]}, etc. Unmatched arguments will be appended to the formatted message in
   *                             square braces. Unmatched placeholders will be left as-is.
   * @param errorMessageArgs     the arguments to be substituted into the message template. Arguments
   *                             are converted to strings using {@link String#valueOf(Object)}.
   * @return the non-null reference that was validated
   * @throws NullPointerException if {@code reference} is null
   */
  public static  T checkNotNull(
      T reference, String errorMessageTemplate, Object... errorMessageArgs) {
    if (reference == null) {
      // If either of these parameters is null, the right thing happens anyway
      throw new NullPointerException(format(errorMessageTemplate, errorMessageArgs));
    }
    return reference;
  }

  /**
   * Substitutes each {@code %s} in {@code template} with an argument. These are matched by
   * position: the first {@code %s} gets {@code args[0]}, etc. If there are more arguments than
   * placeholders, the unmatched arguments will be appended to the end of the formatted message in
   * square braces.
   *
   * @param template a non-null string containing 0 or more {@code %s} placeholders.
   * @param args     the arguments to be substituted into the message template. Arguments are converted
   *                 to strings using {@link String#valueOf(Object)}. Arguments can be null.
   */
  // Note that this is somewhat-improperly used from Verify.java as well.
  static String format(String template, Object... args) {
    template = String.valueOf(template); // null -> "null"

    // start substituting the arguments into the '%s' placeholders
    StringBuilder builder = new StringBuilder(template.length() + 16 * args.length);
    int templateStart = 0;
    int i = 0;
    while (i < args.length) {
      int placeholderStart = template.indexOf("%s", templateStart);
      if (placeholderStart == -1) {
        break;
      }
      builder.append(template, templateStart, placeholderStart);
      builder.append(args[i++]);
      templateStart = placeholderStart + 2;
    }
    builder.append(template, templateStart, template.length());

    // if we run out of placeholders, append the extra args in square braces
    if (i < args.length) {
      builder.append(" [");
      builder.append(args[i++]);
      while (i < args.length) {
        builder.append(", ");
        builder.append(args[i++]);
      }
      builder.append(']');
    }

    return builder.toString();
  }

  /**
   * Ensures the truth of an expression involving one or more parameters to the calling method.
   *
   * @param expression   a boolean expression
   * @param errorMessage the exception message to use if the check fails; will be converted to a
   *                     string using {@link String#valueOf(Object)}
   * @throws IllegalArgumentException if {@code expression} is false
   */
  public static void checkArgument(boolean expression, Object errorMessage) {
    if (!expression) {
      throw new IllegalArgumentException(String.valueOf(errorMessage));
    }
  }

}