com.google.common.base

Class Joiner


  • @GwtCompatible
public class Joiner
extends Object
    An object which joins pieces of text (specified as an array, Iterable, varargs or even a Map) with a separator. It either appends the results to an Appendable or returns them as a String. Example: 
        Joiner joiner = Joiner.on("; ").skipNulls(); . . . return joiner.join("Harry", null, "Ron", "Hermione");

    This returns the string "Harry; Ron; Hermione". Note that all input elements are converted to strings using Object.toString() before being appended.

    If neither skipNulls() nor useForNull(String) is specified, the joining methods will throw NullPointerException if any given element is null.

    Warning: joiner instances are always immutable; a configuration method such as useForNull has no effect on the instance it is invoked on! You must store and use the new joiner instance returned by the method. This makes joiners thread-safe, and safe to store as static final constants. 

        // Bad! Do not do this! Joiner joiner = Joiner.on(','); joiner.skipNulls(); // does nothing! return joiner.join("wrong", null, "wrong");

    See the Guava User Guide article on Joiner.

    Since:
    2.0

    • Nested Class Summary

      Nested Classes

      Modifier and Type Class and Description
      static class  Joiner.MapJoiner
      An object that joins map entries in the same manner as Joiner joins iterables and arrays.

    • Method Summary

      Modifier and Type Method and Description
      <A extends Appendable> A appendTo(A appendable, Iterable<?> parts)
      Appends the string representation of each of parts, using the previously configured separator between each, to appendable.
      <A extends Appendable> A appendTo(A appendable, Iterator<?> parts)
      Appends the string representation of each of parts, using the previously configured separator between each, to appendable.
      <A extends Appendable> A appendTo(A appendable, Object[] parts)
      Appends the string representation of each of parts, using the previously configured separator between each, to appendable.
      <A extends Appendable> A appendTo(A appendable, Object first, Object second, Object... rest)
      Appends to appendable the string representation of each of the remaining arguments.
      StringBuilder appendTo(StringBuilder builder, Iterable<?> parts)
      Appends the string representation of each of parts, using the previously configured separator between each, to builder.
      StringBuilder appendTo(StringBuilder builder, Iterator<?> parts)
      Appends the string representation of each of parts, using the previously configured separator between each, to builder.
      StringBuilder appendTo(StringBuilder builder, Object[] parts)
      Appends the string representation of each of parts, using the previously configured separator between each, to builder.
      StringBuilder appendTo(StringBuilder builder, Object first, Object second, Object... rest)
      Appends to builder the string representation of each of the remaining arguments.
      String join(Iterable<?> parts)
      Returns a string containing the string representation of each of parts, using the previously configured separator between each.
      String join(Iterator<?> parts)
      Returns a string containing the string representation of each of parts, using the previously configured separator between each.
      String join(Object[] parts)
      Returns a string containing the string representation of each of parts, using the previously configured separator between each.
      String join(Object first, Object second, Object... rest)
      Returns a string containing the string representation of each argument, using the previously configured separator between each.
      static Joiner on(char separator)
      Returns a joiner which automatically places separator between consecutive elements.
      static Joiner on(String separator)
      Returns a joiner which automatically places separator between consecutive elements.
      Joiner skipNulls()
      Returns a joiner with the same behavior as this joiner, except automatically skipping over any provided null elements.
      Joiner useForNull(String nullText)
      Returns a joiner with the same behavior as this one, except automatically substituting nullText for any provided null elements.
      Joiner.MapJoiner withKeyValueSeparator(String keyValueSeparator)
      Returns a MapJoiner using the given key-value separator, and the same configuration as this Joiner otherwise.

    • Method Detail

      • on

        public static Joiner on(String separator)
        Returns a joiner which automatically places separator between consecutive elements.

      • on

        public static Joiner on(char separator)
        Returns a joiner which automatically places separator between consecutive elements.

      • appendTo

        public <A extends Appendable> A appendTo(A appendable,
                                         Iterable<?> parts)
                                  throws IOException
        Appends the string representation of each of parts, using the previously configured separator between each, to appendable.
        Throws:
        IOException

      • appendTo

        public <A extends Appendable> A appendTo(A appendable,
                                         Iterator<?> parts)
                                  throws IOException
        Appends the string representation of each of parts, using the previously configured separator between each, to appendable.
        Throws:
        IOException
        Since:
        11.0

      • appendTo

        public final <A extends Appendable> A appendTo(A appendable,
                                               Object[] parts)
                                        throws IOException
        Appends the string representation of each of parts, using the previously configured separator between each, to appendable.
        Throws:
        IOException

      • join

        public final String join(Iterable<?> parts)
        Returns a string containing the string representation of each of parts, using the previously configured separator between each.

      • join

        public final String join(Iterator<?> parts)
        Returns a string containing the string representation of each of parts, using the previously configured separator between each.
        Since:
        11.0

      • join

        public final String join(Object[] parts)
        Returns a string containing the string representation of each of parts, using the previously configured separator between each.

      • join

        public final String join(Object first,
                         Object second,
                         Object... rest)
        Returns a string containing the string representation of each argument, using the previously configured separator between each.

      • useForNull

        public Joiner useForNull(String nullText)
        Returns a joiner with the same behavior as this one, except automatically substituting nullText for any provided null elements.

      • skipNulls

        public Joiner skipNulls()
        Returns a joiner with the same behavior as this joiner, except automatically skipping over any provided null elements.

      • withKeyValueSeparator

        public Joiner.MapJoiner withKeyValueSeparator(String keyValueSeparator)
        Returns a MapJoiner using the given key-value separator, and the same configuration as this Joiner otherwise.