indexOf Case Sensitive?

Question

Is the indexOf(String) method case sensitive? If so, is there a case insensitive version of it?

Answer 1

Yes, indexOf is case sensitive.

The best way to do case insensivity I have found is:

String original;
int idx = original.toLowercase().indexOf(someStr.toLowerCase());

That will do a case insensitive indexOf().

Answer 2

Is the indexOf(String) method case sensitive?

Yes, it is case sensitive:

@Test
public void indexOfIsCaseSensitive() {
    assertTrue("Hello World!".indexOf("Hello") != -1);
    assertTrue("Hello World!".indexOf("hello") == -1);
}

If so, is there a case insensitive version of it?

No, there isn't. You can convert both strings to lower case before calling indexOf:

@Test
public void caseInsensitiveIndexOf() {
    assertTrue("Hello World!".toLowerCase().indexOf("Hello".toLowerCase()) != -1);
    assertTrue("Hello World!".toLowerCase().indexOf("hello".toLowerCase()) != -1);
}

Answer 3

@Test
public void testIndexofCaseSensitive() {
    TestCase.assertEquals(-1, "abcDef".indexOf("d") );
}

Answer 4

The indexOf() methods are all case-sensitive. You can make them case-insensitive by converting your strings to upper/lower case beforehand:

s1 = s1.toLowerCase(Locale.US);
s2 = s2.toLowerCase(Locale.US);
s1.indexOf(s2);

Answer 5

Yes, I am fairly sure it is. One method of working around that using the standard library would be:

int index = str.toUpperCase().indexOf("FOO");

Answer 6

Yes, it is case-sensitive. You can do a case-insensitive indexOf by converting your String and the String parameter both to upper-case before searching.

String str = "Hello world";
String search = "hello";
str.toUpperCase().indexOf(search.toUpperCase());

Answer 7

I've just looked at the source. It compares chars so it is case sensitive.

Answer 8

indexOf is case sensitive. This is because it uses the equals method to compare the elements in the list. The same thing goes for contains and remove.

Answer 9

But it's not hard to write one:

public class CaseInsensitiveIndexOfTest extends TestCase {
    public void testOne() throws Exception {
     assertEquals(2, caseInsensitiveIndexOf("ABC", "xxabcdef"));
    }

    public static int caseInsensitiveIndexOf(String substring, String string) {
     return string.toLowerCase().indexOf(substring.toLowerCase());
    }
}

Answer 10

What are you doing with the index value once returned?

If you are using it to manipulate your string, then could you not use a regular expression instead?

import static org.junit.Assert.assertEquals;    
import org.junit.Test;

public class StringIndexOfRegexpTest {

    @Test
    public void testNastyIndexOfBasedReplace() {
        final String source = "Hello World";
        final int index = source.toLowerCase().indexOf("hello".toLowerCase());
        final String target = "Hi".concat(source.substring(index
                + "hello".length(), source.length()));
        assertEquals("Hi World", target);
    }

    @Test
    public void testSimpleRegexpBasedReplace() {
        final String source = "Hello World";
        final String target = source.replaceFirst("(?i)hello", "Hi");
        assertEquals("Hi World", target);
    }
}