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    • com.google.common.base.Absent Maven / Gradle / Ivy

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    This artifact provides a single jar that contains all classes required to use remote Jakarta Enterprise Beans and Jakarta Messaging, including all dependencies. It is intended for use by those not using maven, maven users should just import the Jakarta Enterprise Beans and Jakarta Messaging BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

    There is a newer version: 35.0.0.Beta1
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    /*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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 com.google.common.base;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;

import java.util.Collections;
import java.util.Set;

import javax.annotation.Nullable;

/**
 * Implementation of an {@link Optional} not containing a reference.
 */
@GwtCompatible
final class Absent extends Optional {
  static final Absent INSTANCE = new Absent();

  @SuppressWarnings("unchecked") // implementation is "fully variant"
  static  Optional withType() {
    return (Optional) INSTANCE;
  }

  private Absent() {}

  @Override public boolean isPresent() {
    return false;
  }

  @Override public T get() {
    throw new IllegalStateException("Optional.get() cannot be called on an absent value");
  }

  @Override public T or(T defaultValue) {
    return checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
  }

  @SuppressWarnings("unchecked") // safe covariant cast
  @Override public Optional or(Optional secondChoice) {
    return (Optional) checkNotNull(secondChoice);
  }

  @Override public T or(Supplier supplier) {
    return checkNotNull(supplier.get(),
        "use Optional.orNull() instead of a Supplier that returns null");
  }

  @Override @Nullable public T orNull() {
    return null;
  }

  @Override public Set asSet() {
    return Collections.emptySet();
  }

  @Override public  Optional transform(Function function) {
    checkNotNull(function);
    return Optional.absent();
  }

  @Override public boolean equals(@Nullable Object object) {
    return object == this;
  }

  @Override public int hashCode() {
    return 0x598df91c;
  }

  @Override public String toString() {
    return "Optional.absent()";
  }

  private Object readResolve() {
    return INSTANCE;
  }

  private static final long serialVersionUID = 0;
}
    
    
    
    

    




    
    
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