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Java 8 StringJoiner

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Java StringJoiner

Java added a new final class StringJoiner in java.util package. It is used to construct a sequence of characters separated by a delimiter. Now, you can create string by passing delimiters like comma(,), hyphen(-) etc. You can also pass prefix and suffix to the char sequence.

StringJoiner Constructors

Constructor Description
Public StringJoiner(CharSequence delimiter) It constructs a StringJoiner with no characters in it, with no prefix or suffix, and a copy of the supplied delimiter. It throws NullPointerException if delimiter is null.
Public StringJoiner(CharSequence delimiter,CharSequence prefix,CharSequence suffix) It constructs a StringJoiner with no characters in it using copies of the supplied prefix, delimiter and suffix. It throws NullPointerException if prefix, delimiter, or suffix is null.

StringJoiner Methods

Method Description
Public StringJoiner add(CharSequence newElement) It adds a copy of the given CharSequence value as the next element of the StringJoiner value. If newElement is null,”null” is added.
Public StringJoiner merge(StringJoiner other) It adds the contents of the given StringJoiner without prefix and suffix as the next element if it is non-empty. If the given StringJoiner is empty, the call has no effect.
Public int length() It returns the length of the String representation of this StringJoiner.
Public StringJoiner setEmptyValue(CharSequence emptyValue) It sets the sequence of characters to be used when determining the string representation of this StringJoiner and no elements have been added yet, that is, when it is empty.

Java StringJoiner Example



Java StringJoiner Example: adding prefix and suffix



StringJoiner Example: Merge Two StringJoiner

The merge() method merges two StringJoiner objects excluding of prefix and suffix of second StringJoiner object.



StringJoiner Example: StringJoiner Methods


 It is empty Rahul,Raju Length: 10 Rahul,Raju Character at index 3: u Rahul,Raju,Sorabh New Length: 17 
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