gistfile1.java

final Joiner joiner = Joiner.on(",")
                .skipNulls();
StringBuilder builder = new StringBuilder();
final String[] input1 = new String[] {"dave", "john"};

builder = joiner.appendTo(builder, input1);

// Dave and John have a comma between them.

final String[] input2 = new String[]{null, "dan"};
builder = joiner.appendTo(builder, input2);

// The string is now "dave,johndan".

final String[] input3 = new String[]{"matt", "sam"};
final String result = joiner.appendTo(builder, input3).toString();

// And finally we will have "dave, johndanmatt,sam".
// result = dave,johndanmatt,sam