Apex String Methods with Examples

Strings are everywhere in Salesforce code: names, emails, phone numbers, external Ids, JSON, error messages. The String class has dozens of methods; this lesson focuses on the ones you'll use every week, grouped by job, plus two behaviours that catch out developers coming from Java.

Comparing strings

String a = 'Acme';
String b = 'ACME';

System.debug('a == b: ' + (a == b));                     // case-insensitive!
System.debug('a.equals(b): ' + a.equals(b));             // case-sensitive
System.debug('equalsIgnoreCase: ' + a.equalsIgnoreCase(b));
System.debug('compareTo: ' + 'apple'.compareTo('banana'));   // negative: comes first

// sets and map keys ARE case-sensitive
Set<String> names = new Set<String>{ 'Acme' };
System.debug('set contains ACME? ' + names.contains('ACME'));

a == b: true
a.equals(b): false
equalsIgnoreCase: true
compareTo: -1
set contains ACME? false

Checking for empty values

String nothing = null;
String empty = '';
String spaces = '   ';

System.debug('isBlank:    ' + String.isBlank(nothing) + ' ' + String.isBlank(empty) + ' ' + String.isBlank(spaces));
System.debug('isEmpty:    ' + String.isEmpty(nothing) + ' ' + String.isEmpty(empty) + ' ' + String.isEmpty(spaces));
System.debug('isNotBlank: ' + String.isNotBlank('Acme'));

// the static methods are null-safe; instance methods on null throw
try {
    Integer len = nothing.length();
} catch (NullPointerException e) {
    System.debug('NullPointerException on nothing.length()');
}
System.debug('Default: ' + (String.isBlank(nothing) ? 'N/A' : nothing));

isBlank:    true true true
isEmpty:    true true false
isNotBlank: true
NullPointerException on nothing.length()
Default: N/A

Use String.isBlank() for validation – it treats null, empty and whitespace-only the same, which is almost always what you want for user input.

Searching, extracting and replacing

String email = '  Ravi.Kumar@Example.COM ';
String clean = email.trim().toLowerCase();
System.debug(clean);

System.debug('contains @: ' + clean.contains('@'));
System.debug('domain: ' + clean.substringAfter('@'));
System.debug('user: ' + clean.substringBefore('@'));
System.debug('ends with .com: ' + clean.endsWith('.com'));
System.debug('index of dot: ' + clean.indexOf('.'));

String invoice = 'INV-2026-00042';
System.debug('year: ' + invoice.substring(4, 8));
System.debug('last 5: ' + invoice.right(5) + ', first 3: ' + invoice.left(3));
System.debug('number: ' + Integer.valueOf(invoice.substringAfterLast('-')));

String phone = '+91 (98765) 43210';
System.debug('digits only: ' + phone.replaceAll('[^0-9]', ''));
System.debug(invoice.replace('INV', 'CRN'));

ravi.kumar@example.com
contains @: true
domain: example.com
user: ravi.kumar
ends with .com: true
index of dot: 4
year: 2026
last 5: 00042, first 3: INV
number: 42
digits only: 919876543210
CRN-2026-00042

replace works on plain text; replaceAll and split take a regular expression, so characters like ., | and + have special meaning – which leads to the next gotcha.

Splitting, joining and formatting

String tags = 'apex, soql ,  dml,,triggers';
List<String> parts = new List<String>();
for (String t : tags.split(',')) {
    if (String.isNotBlank(t)) parts.add(t.trim());
}
System.debug(parts);
System.debug(String.join(parts, ' | '));

// split takes a regex: escape special characters
System.debug('split on "." gives ' + 'v1.2.3'.split('.').size() + ' parts (regex: any character)');
System.debug('escaped dot gives ' + 'v1.2.3'.split('\\.').size() + ' parts');

// String.format fills numbered placeholders
String msg = String.format('Hi {0}, your case {1} is {2}.', new List<Object>{ 'Neha', '00001042', 'Closed' });
System.debug(msg);

System.debug('acme corp'.capitalize() + ' | ' + 'Long description text'.abbreviate(12));
System.debug('7'.leftPad(4, '0') + ' | ' + 'abc'.reverse() + ' | ' + 'na'.repeat(3));
System.debug('   too    many   spaces  '.normalizeSpace());

(apex, soql, dml, triggers)
apex | soql | dml | triggers
split on "." gives 0 parts (regex: any character)
escaped dot gives 3 parts
Hi Neha, your case 00001042 is Closed.
Acme corp | Long desc...
0007 | cba | nanana
too many spaces

Building long strings

Strings are immutable: every += creates a new String. For a few pieces that's fine; for thousands of lines (a CSV export) collect parts in a list and join once – it's faster and uses less heap:

List<String> rows = new List<String>{ 'Name,Industry' };
for (Integer i = 1; i <= 3; i++) {
    rows.add('Account ' + i + ',Technology');
}
String csv = String.join(rows, '\n');
System.debug(csv);
System.debug('Length: ' + csv.length());

Name,Industry
Account 1,Technology
Account 2,Technology
Account 3,Technology
Length: 76

Escaping

• Inside a string literal, escape a single quote as \' and a backslash as \\; \n is a newline.
• Never build SOQL from user input by concatenation. Use bind variables – or at least String.escapeSingleQuotes(input) (see dynamic SOQL).
• escapeHtml4(), escapeCsv() and escapeEcmaScript() exist for output in those formats.

Practice

Summary