本文整理了Java中com.google.common.base.Optional.isPresent()方法的一些代码示例，展示了Optional.isPresent()的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Optional.isPresent()方法的具体详情如下：
包路径：com.google.common.base.Optional
类名称：Optional
方法名：isPresent

Optional.isPresent介绍

[英]Returns true if this holder contains a (non-null) instance.

Comparison to java.util.Optional: no differences.
[中]如果此持有者包含（非空）实例，则返回true。
与java的比较。util。可选：无差异。

代码示例

代码示例来源：origin: google/guava

/**
 * If a value is present in {@code optional}, returns a stream containing only that element,
 * otherwise returns an empty stream.
 */
public static <T> Stream<T> stream(com.google.common.base.Optional<T> optional) {
 return optional.isPresent() ? Stream.of(optional.get()) : Stream.of();
}

代码示例来源：origin: google/guava

@Override
public Optional<Long> sizeIfKnown() {
 Optional<Long> optionalUnslicedSize = ByteSource.this.sizeIfKnown();
 if (optionalUnslicedSize.isPresent()) {
  long unslicedSize = optionalUnslicedSize.get();
  long off = Math.min(offset, unslicedSize);
  return Optional.of(Math.min(length, unslicedSize - off));
 }
 return Optional.absent();
}

代码示例来源：origin: apache/incubator-druid

@Override
public Optional<ByteSource> streamTaskLog(String taskid, long offset) throws IOException
{
 for (TaskLogStreamer provider : providers) {
  final Optional<ByteSource> stream = provider.streamTaskLog(taskid, offset);
  if (stream.isPresent()) {
   return stream;
  }
 }
 return Optional.absent();
}

代码示例来源：origin: apache/incubator-shardingsphere

private static void changeColumnDefinitionPosition(final ColumnFirstPositionSegment columnFirstPositionSegment, final List<ColumnMetaData> columnMetaDataList) {
  Optional<ColumnMetaData> columnMetaData = find(columnFirstPositionSegment.getColumnName(), columnMetaDataList);
  if (columnMetaData.isPresent()) {
    columnMetaDataList.remove(columnMetaData.get());
    columnMetaDataList.add(0, columnMetaData.get());
  }
}

代码示例来源：origin: apache/incubator-shardingsphere

/**
 * Parse order by.
 *
 * @param selectStatement select statement
 */
public final void parse(final SelectStatement selectStatement) {
  if (!lexerEngine.skipIfEqual(DefaultKeyword.ORDER)) {
    return;
  }
  List<OrderItem> result = new LinkedList<>();
  lexerEngine.skipIfEqual(OracleKeyword.SIBLINGS);
  lexerEngine.accept(DefaultKeyword.BY);
  do {
    Optional<OrderItem> orderItem = parseSelectOrderByItem(selectStatement);
    if (orderItem.isPresent()) {
      result.add(orderItem.get());
    }
  } while (lexerEngine.skipIfEqual(Symbol.COMMA));
  selectStatement.getOrderByItems().addAll(result);
}

代码示例来源：origin: apache/incubator-shardingsphere

private SelectItem getAggregationDistinctSelectItem(final SelectStatement selectStatement, 
                          final AggregationType aggregationType, final int beginPosition, final int endPosition, final String innerExpression) {
  Optional<String> alias = aliasExpressionParser.parseSelectItemAlias().isPresent() ? aliasExpressionParser.parseSelectItemAlias() 
      : Optional.of(DerivedAlias.AGGREGATION_DISTINCT_DERIVED.getDerivedAlias(selectStatement.getAggregationDistinctSelectItems().size()));
  AggregationDistinctSelectItem result = new AggregationDistinctSelectItem(
      aggregationType, innerExpression, alias, getDistinctColumnName(innerExpression));
  selectStatement.getSQLTokens().add(new AggregationDistinctToken(beginPosition, endPosition - 1, result.getDistinctColumnName(), alias));
  return result;
}

代码示例来源：origin: apache/incubator-shardingsphere

@Override
  public void fill(final TableSegment sqlSegment, final SQLStatement sqlStatement, final String sql, final ShardingRule shardingRule, final ShardingTableMetaData shardingTableMetaData) {
    boolean fill = false;
    String tableName = sqlSegment.getName();
    if (shardingRule.contains(tableName) || shardingRule.isBroadcastTable(tableName) || shardingRule.findBindingTableRule(tableName).isPresent()
        || shardingRule.getShardingDataSourceNames().getDataSourceNames().contains(shardingRule.getShardingDataSourceNames().getDefaultDataSourceName())) {
      fill = true;
    } else {
      if (!(sqlStatement instanceof SelectStatement) && sqlStatement.getTables().isEmpty()) {
        fill = true;
      }
    }
    if (fill) {
      sqlStatement.getTables().add(new Table(sqlSegment.getName(), sqlSegment.getAlias()));
      sqlStatement.getSQLTokens().add(sqlSegment.getToken());
    }
  }
}

代码示例来源：origin: dreamhead/moco

@Override
  protected Optional<String> doExtract(final HttpRequest request) {
    Optional<ImmutableMap<String, String>> forms = extractor.extract(request);
    if (forms.isPresent()) {
      return fromNullable(forms.get().get(key));
    }

    return Optional.absent();
  }
}

代码示例来源：origin: apache/incubator-shardingsphere

/**
 *  Extract expression.
 *
 * @param placeholderIndexes  place holder index
 * @param expressionNode expression node
 * @return expression segment
 */
public Optional<? extends ExpressionSegment> extract(final Map<ParserRuleContext, Integer> placeholderIndexes, final ParserRuleContext expressionNode) {
  Optional<ParserRuleContext> subqueryNode = ExtractorUtils.findFirstChildNode(expressionNode, RuleName.SUBQUERY);
  return subqueryNode.isPresent() ? new SubqueryExtractor().extract(subqueryNode.get()) : Optional.of(extractExpression(placeholderIndexes, expressionNode));
}

代码示例来源：origin: apache/incubator-shardingsphere

@Override
  public Optional<DropPrimaryKeySegment> extract(final ParserRuleContext ancestorNode) {
    return ExtractorUtils.findFirstChildNode(ancestorNode, RuleName.DROP_PRIMARY_KEY).isPresent() ? Optional.of(new DropPrimaryKeySegment()) : Optional.<DropPrimaryKeySegment>absent();
  }
}

代码示例来源：origin: google/guava

public void testIsPresent_yes() {
 assertTrue(Optional.of("training").isPresent());
}

代码示例来源：origin: google/guava

@Override
public Optional<Long> lengthIfKnown() {
 long result = 0L;
 for (CharSource source : sources) {
  Optional<Long> lengthIfKnown = source.lengthIfKnown();
  if (!lengthIfKnown.isPresent()) {
   return Optional.absent();
  }
  result += lengthIfKnown.get();
 }
 return Optional.of(result);
}

代码示例来源：origin: apache/incubator-shardingsphere

private static void changeColumnDefinitionPosition(final ColumnAfterPositionSegment columnAfterPositionSegment, final List<ColumnMetaData> columnMetaDataList) {
  Optional<ColumnMetaData> columnMetaData = find(columnAfterPositionSegment.getColumnName(), columnMetaDataList);
  Optional<ColumnMetaData> afterColumnMetaData = find(columnAfterPositionSegment.getAfterColumnName(), columnMetaDataList);
  if (columnMetaData.isPresent() && afterColumnMetaData.isPresent()) {
    columnMetaDataList.remove(columnMetaData.get());
    columnMetaDataList.add(columnMetaDataList.indexOf(afterColumnMetaData.get()) + 1, columnMetaData.get());
  }
}

代码示例来源：origin: apache/incubator-druid

private <T> Response asLeaderWith(Optional<T> x, Function<T, Response> f)
{
 if (x.isPresent()) {
  return f.apply(x.get());
 } else {
  // Encourage client to try again soon, when we'll likely have a redirect set up
  return Response.status(Response.Status.SERVICE_UNAVAILABLE).build();
 }
}

代码示例来源：origin: apache/incubator-shardingsphere

private Optional<OrConditionSegment> buildCondition(final ParserRuleContext node, final Map<ParserRuleContext, Integer> placeholderIndexes) {
    Optional<ParserRuleContext> exprNode = ExtractorUtils.findFirstChildNode(node, RuleName.EXPR);
    return exprNode.isPresent() ? predicateSegmentExtractor.extractCondition(placeholderIndexes, exprNode.get()) : Optional.<OrConditionSegment>absent();
  }
}

代码示例来源：origin: apache/incubator-shardingsphere

@Override
  public Optional<SubqueryConditionSegment> extract(final ParserRuleContext ancestorNode) {
    Collection<ParserRuleContext> suQueryNodes = ExtractorUtils.getAllDescendantNodes(ancestorNode, RuleName.SUBQUERY);
    SubqueryConditionSegment result = new SubqueryConditionSegment();
    FromWhereExtractor fromWhereExtractor = new FromWhereExtractor();
    for (ParserRuleContext each : suQueryNodes) {
      Optional<FromWhereSegment> condition = fromWhereExtractor.extract(each, ancestorNode);
      if (condition.isPresent()) {
        result.getOrConditions().add(condition.get().getConditions());
      }
    }
    return Optional.of(result);
  }
}

代码示例来源：origin: apache/incubator-druid

@Override
 public Optional<ByteSource> streamTaskReports(String taskid) throws IOException
 {
  for (TaskLogStreamer provider : providers) {
   final Optional<ByteSource> stream = provider.streamTaskReports(taskid);
   if (stream.isPresent()) {
    return stream;
   }
  }

  return Optional.absent();
 }
}

代码示例来源：origin: apache/incubator-shardingsphere

/**
 * Find actual default data source name.
 *
 * <p>If use master-slave rule, return master data source name.</p>
 *
 * @return actual default data source name
 */
public Optional<String> findActualDefaultDataSourceName() {
  String defaultDataSourceName = shardingDataSourceNames.getDefaultDataSourceName();
  if (Strings.isNullOrEmpty(defaultDataSourceName)) {
    return Optional.absent();
  }
  Optional<String> masterDefaultDataSourceName = findMasterDataSourceName(defaultDataSourceName);
  return masterDefaultDataSourceName.isPresent() ? masterDefaultDataSourceName : Optional.of(defaultDataSourceName);
}

代码示例来源：origin: google/j2objc

@Override
public Optional<Long> lengthIfKnown() {
 long result = 0L;
 for (CharSource source : sources) {
  Optional<Long> lengthIfKnown = source.lengthIfKnown();
  if (!lengthIfKnown.isPresent()) {
   return Optional.absent();
  }
  result += lengthIfKnown.get();
 }
 return Optional.of(result);
}

代码示例来源：origin: google/guava

for (Class<?> cls : classes) {
 Optional<String> testedClassName = TEST_SUFFIX.chop(cls.getName());
 if (testedClassName.isPresent()) {
  Class<?> testedClass = classMap.get(testedClassName.get());
  if (testedClass != null) {
   testClasses.put(testedClass, cls);
 result.add(candidate);