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title: “MapElements”

MapElements

Applies a simple 1-to-1 mapping function over each element in the collection.

Examples

Example 1: providing the mapping function using a SimpleFunction

{{< highlight java >}} PCollection lines = Create.of(“Hello World”, “Beam is fun”); PCollection lineLengths = lines.apply(MapElements.via( new SimpleFunction<String, Integer>() { @Override public Integer apply(String line) { return line.length(); } }); {{< /highlight >}}

Example 2: providing the mapping function using a SerializableFunction, which allows the use of Java 8 lambdas. Due to type erasure, you need to provide a hint indicating the desired return type.

{{< highlight java >}} PCollection lines = Create.of(“Hello World”, “Beam is fun”); PCollection lineLengths = lines.apply(MapElements .into(TypeDescriptors.integers()) .via((String line) -> line.length())); {{< /highlight >}}

Related transforms

• FlatMapElements behaves the same as Map, but for each input it may produce zero or more outputs.
• Filter is useful if the function is just deciding whether to output an element or not.
• ParDo is the most general element-wise mapping operation, and includes other abilities such as multiple output collections and side-inputs.