Difference between isEmpty() and zero length

Question

What is the difference between these two methods?

public boolean nameControl(String str) 
{
    if (str.trim().isEmpty()) return false;
    if (str.trim().length() == 0) return false;
    return true;
}

I need find out that str should have at least one character.

Have you tried it? Have you looked at the source code? Have you looked at the javadoc? — Sotirios Delimanolis, Oct 01 '13 at 21:36
Nothing is different, only that one is explicitly checked where as isEmpty does the same under the hood. — BlackBox, Oct 01 '13 at 21:38
If your primary question is how to check whether a string is empty, then [Checking for empty strings](http://stackoverflow.com/q/16865521/1281433) is a possible duplicate. You might also be interested in [Should I use string.isEmpty() or “”.equals(string)?](http://stackoverflow.com/q/3321526/1281433). — Joshua Taylor, Oct 01 '13 at 21:42

score 19 · Accepted Answer · answered Oct 01 '13 at 21:38

19

There is no real difference between them.

Javadocs for isEmpty()

Returns true if, and only if, length() is 0.

answered Oct 01 '13 at 21:38

rgettman

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score 4 · Answer 2 · edited Jun 20 '20 at 09:12

4

From the Javadoc:

isEmpty

public boolean isEmpty()

Returns true if, and only if, length() is 0.

edited Jun 20 '20 at 09:12

Community

1
1

answered Oct 01 '13 at 21:38

djechlin

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score 4 · Answer 3 · edited Jun 20 '20 at 09:12

4

For Java 6+

isEmpty() works since Java 6 and length == 0 works since Java 1.2+ or possibly an older version.

If you notice, the implementation of the method

Apache Commons Lang (for Java 5+)

public static boolean isEmpty(String str)

of the class org.apache.commons.lang.StringUtils from Apache Commons Lang use str.length() == 0 in order to support Java 5.0+.

edited Jun 20 '20 at 09:12

Community

1
1

answered Oct 01 '13 at 22:01

Paul Vargas

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score 1 · Answer 4 · answered Oct 01 '13 at 21:39

1

Luckily for you this is already documented:

IsEmpty(): http://docs.oracle.com/javase/6/docs/api/java/lang/String.html#isEmpty()

Length(): http://docs.oracle.com/javase/6/docs/api/java/lang/String.html#length()

answered Oct 01 '13 at 21:39

Davie Brown

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Christopher · Answer 5 · 2013-10-01T21:57:30.240

0

If you need to detect if a string has at least one (non-whitespace) character, I would try:

public boolean nameControl(String str) {
    if (str == null) return false;
    else if (str.trim().length() == 0) return false;
    return true;
}

If a string containing only whitespace should return true I would remove the trim as follows:

public boolean nameControl(String str) {
    if (str == null) return false;
    else if (str.length() == 0) return false;
    return true;
}

edited Oct 01 '13 at 21:57

answered Oct 01 '13 at 21:40

Christopher

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By definition, isn't any form of whitespace a character? – Obicere Oct 01 '13 at 21:43
Based on the original posters use of trim, I had made the assumption that a string containing only whitespace should return false. I have updated the answer to reflect both scenarios. – Christopher Oct 01 '13 at 21:59

score 0 · Answer 6 · answered Sep 12 '18 at 19:11

0

Wanted to update on this:

I Observed if the string is having newline char(\n or \r), that time length fun gives you not zero value but isEmpty fun standout with value as true which is expected.

answered Sep 12 '18 at 19:11

Indrajeet Gour

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Difference between isEmpty() and zero length

6 Answers6

For Java 6+

Apache Commons Lang (for Java 5+)