How do I convert underscore into human-readable names in Java?

Question

I'd like to write a method that converts CamelCase into a human-readable name. This is very similar to this question but now with underscore.

Here's the test case:

public void testSplitUnderscore() {
    assertEquals("lowercase", splitUnderscore("lowercase"));
    assertEquals("Class", splitUnderscore("Class"));
    assertEquals("My Class", splitUnderscore("My_Class"));
    assertEquals("HTML", splitUnderscore("HTML"));
    assertEquals("PDF Loader", splitUnderscore("PDF_Loader"));
    assertEquals("A String", splitUnderscore("A_String"));
    assertEquals("Simple XML Parser", splitUnderscore("Simple_XML_Parser"));
    assertEquals("GL 11 Version", splitUnderscore("GL_11_Version"));
    assertEquals("99 Bottles", splitUnderscore("99_Bottle"));
    assertEquals("May 5", splitUnderscore("May_5"));
    assertEquals("BFG 9000", splitUnderscore("BFG_9000"));
    assertEquals("beginning", splitUnderscore("_beginning"));
    assertEquals("end", splitUnderscore("end_"));
    assertEquals("double middle", splitUnderscore("double__middle"));
    assertEquals("double end", splitUnderscore("double_end__"));
    assertEquals("double start", splitUnderscore("__double_start"));
    assertEquals("double start middle end", splitUnderscore("__double_start__middle_end__"));
}

Check out [Apache Commons](http://commons.apache.org/) ... DRY. — Edward J Beckett, Sep 29 '16 at 01:22
DRY ~ Dont Repeat Yourself :) ~ Apache commons already has those utilities. — Edward J Beckett, Sep 30 '16 at 18:32

Matthew Diana · Accepted Answer · 2016-09-29T05:36:38.913

4

A naive way of accomplishing this would be to replace every '_' with a ' ', and then trim the whitespaces off the final string:

public static String splitUnderscore(String s) {
    return s.replace("_", " ").trim();
}

While the above works for most cases, to handle multiple adjacent underscores we could use a regular expression to replace any number of consecutive underscores with a single ' ':

public static String splitUnderscore(String s) {
    return s.replaceAll("_{1,}", " ").trim();
}

edited Sep 29 '16 at 05:36

answered Sep 29 '16 at 01:23

Matthew Diana

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This will pass your test cases. – Samuel Thompson Sep 29 '16 at 01:49
How can this work with the extra double underscores? – Whitecat Sep 29 '16 at 04:33

score 2 · Answer 2 · edited Sep 29 '16 at 01:41

2

The following should work:

String.replace('_', " ").trim();

edited Sep 29 '16 at 01:41

Meik Vtune

450
8
25

answered Sep 29 '16 at 01:25

Mr. Negi

154
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15

score 1 · Answer 3 · answered Sep 29 '16 at 04:04

1

You should have a couple more test cases:

assertEquals("A String", splitUnderscore("double__middle"));
assertEquals("A String", splitUnderscore("double_end__"));
assertEquals("A String", splitUnderscore("__double_start"));
assertEquals("A String", splitUnderscore("__double_start__middle_end__"));

answered Sep 29 '16 at 04:04

Graham H

125
12

Added the extra tests to the question. – Whitecat Sep 29 '16 at 04:32

How do I convert underscore into human-readable names in Java?

3 Answers3