Inspecting Strings

A String can tell you a lot about itself before you change anything. Apex gives you a set of inspection methods that answer simple questions: how long is it, is there anything in it, does it hold a certain piece of text.

How Long Is It

length() returns the number of characters:

String code = 'LC-1234';
System.debug(code.length()); // 7

Is There Anything In It

isEmpty() is true only when the string has zero characters. isBlank() is true when the value is null, empty, or only whitespace, which makes it the safer everyday check:

System.debug(String.isEmpty('')); // true
System.debug(String.isBlank('   ')); // true
System.debug(String.isBlank(null)); // true

Both are static methods on String, so they accept a null value without throwing.

Does It Contain This

String fileName = 'quarterly-report.pdf';
System.debug(fileName.contains('report')); // true
System.debug(fileName.startsWith('quarterly')); // true
System.debug(fileName.endsWith('.pdf')); // true

Where Is It

indexOf() returns the position of the first match, counting from zero, or -1 when there is no match at all:

System.debug(fileName.indexOf('.')); // 16
System.debug(fileName.indexOf('zzz')); // -1

Common Mistakes

Calling an instance method such as length() on a null string throws a null pointer exception. Guard with String.isBlank(value) first, because that static method handles null safely.

Why This Matters

Validation is inspection. Nearly every check on user input starts by asking whether the text is present, long enough, and shaped the way you expect.