[LANG-647] ToStringBuilder output makes it difficult to distinguish between an empty String array and an array of one empty String

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.5
• Fix Version/s: Patch Needed
• Component/s: lang.builder.*
• Assignee: Unassigned
• Reporter: pascal jacob
• Created: 25/Aug/10 09:42
• Updated: 19/Apr/17 16:01

Description

ToStringBuilder output is the same for an empty array (i.e. new String[0]) and for an array containing only a single empty string (i.e. new String[]

{ "" } ). This makes it difficult in some case to see the true nature of arrays.

For example I once had a JUnit test case that print the following trace failure:
java.lang.AssertionError:
Expected: <InputViewHelper[a={},b={},c={msg},d={time}>
got: <InputViewHelper[a={},b={},c={msg},d={time}>

Apparently the two objects look like the same! But they are not: one had an empty array; the other had an array with only a single empty string. With a customized ToStringStyle the difference became apparent:
Expected: <InputViewHelper[a={},b={},c={msg},d={time}>
got: <InputViewHelper[a={""},b={},c={msg},d={time}>


The fix is simple, change the method: protected void appendDetail(StringBuffer buffer, String fieldName, Object value) to:
protected void appendDetail(StringBuffer buffer, String fieldName, Object value) {
if((value instanceof String) && ((String)value).isEmpty()) { buffer.append("\"\""); }
else { super.appendDetail(buffer, fieldName, value); }
}

here is the test case that revealed the problem:
public void testToStringBuilder() {
ToStringBuilder builder1 = new ToStringBuilder("Builder1");
builder1.append("empty array", new String[0]);
builder1.append("array of one empty string", new String[] { "" }

);
builder1.append("array of two empty strings", new String[]

{ "", "" });
String builder1Result = builder1.toString();
System.out.println(builder1Result);
// -----
ToStringBuilder builder2 = new ToStringBuilder("Builder2", new ToStringStyle() {
@Override
protected void appendDetail(StringBuffer buffer, String fieldName, Object value) {
if((value instanceof String) && ((String)value).isEmpty()) { buffer.append("\"\""); }
else { super.appendDetail(buffer, fieldName, value); }
}
});
builder2.append("empty array", new String[0]);
builder2.append("array of one empty string", new String[] { "" });
builder2.append("array of two empty strings", new String[] { "", "" }

);
String builder2Result = builder2.toString();
System.out.println(builder2Result);
}