[jira] Created: (LANG-643) Javadoc StringUtils.left() claims to throw on negative len, but doesn't

[Volker Glave (JIRA)]

Javadoc StringUtils.left() claims to throw on negative len, but doesn't
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                 Key: LANG-643
                 URL: https://issues.apache.org/jira/browse/LANG-643
             Project: Commons Lang
          Issue Type: Bug
          Components: lang.*
    Affects Versions: 2.5, 3.0
            Reporter: Volker Glave
            Priority: Minor


The Javadoc comment for StringUtils.left() claims to throw an exception "if len 
is negative" (and that input argument len "must be zero or positive"):

http://commons.apache.org/lang/api/org/apache/commons/lang3/StringUtils.html#left(java.lang.String,%20int)
http://commons.apache.org/lang/api-2.5/org/apache/commons/lang/StringUtils.html#left(java.lang.String,%20int)

{quote}public static String left(String str, int len)

    Gets the leftmost len characters of a String.

    If len characters are not available, or the String is null, the String will 
be returned without an exception. {color:red}An exception is thrown if len is 
negative.{color}

     StringUtils.left(null, *)    = null
     StringUtils.left(*, -ve)     = ""
     StringUtils.left("", *)      = ""
     StringUtils.left("abc", 0)   = ""
     StringUtils.left("abc", 2)   = "ab"
     StringUtils.left("abc", 4)   = "abc"

    Parameters:
        str - the String to get the leftmost characters from, may be null
        len - the length of the required String, {color:red}must be zero or 
positive{color}
    Returns:
        the leftmost characters, null if null String input{quote}

But it  doesn't. (Luckily and preferably anyway :-).)
Instead an empty string will be returned. (Which is good.) As is seen from the 
implementation code ...

{code}........
        if (len < 0) {
            return EMPTY;
        }
        ...{code}

..., and by example, too:

{code}$ cat StringUtilsTest.java
import org.apache.commons.lang.StringUtils;

public final class StringUtilsTest {
    public static void main(final String[] args) {
        final String result = StringUtils.left("foobar", -42);
        System.out.println(">" + result + "<");
    }
}

$ javac -classpath commons-lang.jar StringUtilsTest.java

$ java -classpath .:commons-lang.jar StringUtilsTest
><{code}

The Javadoc comment should by updated.

Same issue for right() and mid(), by the way.

Volker Glave

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