Class Joiner

java.lang.Object
com.google.common.base.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
Author:
Kevin Bourrillion

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static final 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
    Description
    final <A extends Appendable>
    A
    appendTo(A appendable, @Nullable Object[] parts)
    Appends the string representation of each of parts, using the previously configured separator between each, to appendable.
    final <A extends Appendable>
    A
    appendTo(A appendable, @Nullable Object first, @Nullable Object second, @Nullable Object... rest)
    Appends to appendable the string representation of each of the remaining arguments.
    <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.
    final StringBuilder
    appendTo(StringBuilder builder, @Nullable Object[] parts)
    Appends the string representation of each of parts, using the previously configured separator between each, to builder.
    final StringBuilder
    appendTo(StringBuilder builder, @Nullable Object first, @Nullable Object second, @Nullable Object... rest)
    Appends to builder the string representation of each of the remaining arguments.
    final StringBuilder
    appendTo(StringBuilder builder, Iterable<?> parts)
    Appends the string representation of each of parts, using the previously configured separator between each, to builder.
    final StringBuilder
    appendTo(StringBuilder builder, Iterator<?> parts)
    Appends the string representation of each of parts, using the previously configured separator between each, to builder.
    final String
    join(@Nullable Object[] parts)
    Returns a string containing the string representation of each of parts, using the previously configured separator between each.
    final String
    join(@Nullable Object first, @Nullable Object second, @Nullable Object... rest)
    Returns a string containing the string representation of each argument, using the previously configured separator between each.
    String
    join(Iterable<?> parts)
    Returns a string containing the string representation of each of parts, using the previously configured separator between each.
    final String
    join(Iterator<?> parts)
    Returns a string containing the string representation of each of parts, 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(char keyValueSeparator)
    Returns a MapJoiner using the given key-value separator, and the same configuration as this Joiner otherwise.
    Joiner.MapJoiner
    withKeyValueSeparator(String keyValueSeparator)
    Returns a MapJoiner using the given key-value separator, and the same configuration as this Joiner otherwise.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait