Sequences.java

gistfile1.txt

package com.truward.polymer.util;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;

import javax.annotation.Nonnull;
import java.util.*;

/**
 * Static utility methods for working with collections.
 * Defines a set of 
 *
 * @author Alexander Shabanov
 */
public final class Sequences {
  /** Hidden */
  private Sequences() {}

  @Nonnull public static <T> List<T> join(@Nonnull List<? extends T> source, @Nonnull T element) {
    final int size = source.size();
    if (size == 0) {
      return ImmutableList.of(element);
    } else if (size == 1) {
      return ImmutableList.of(source.get(0), element);
    }

    // non-cheap operation - make list
    final List<T> result = new ArrayList<>(size + 1);
    result.addAll(source);
    result.add(element);
    return ImmutableList.copyOf(result);
  }

  @Nonnull public static <T> Set<T> join(@Nonnull Set<? extends T> source, @Nonnull T element) {
    final int size = source.size();
    if (size == 0) {
      return ImmutableSet.of(element);
    }

    // non-cheap operation - make list
    final List<T> result = new ArrayList<>(size + 1);
    result.addAll(source);
    result.add(element);
    return ImmutableSet.copyOf(result);
  }

  @Nonnull public static <K, V> Map<K, V> join(@Nonnull Map<? extends K, ? extends V> source,
                                               @Nonnull K key,
                                               @Nonnull V value) {
    final int size = source.size();
    if (size == 0) {
      return ImmutableMap.of(key, value);
    }

    // non-cheap operation - make list
    final Map<K, V> result = new LinkedHashMap<>();
    result.putAll(source);
    result.put(key, value);
    return ImmutableMap.copyOf(result);
  }
}