Common String Methods · Java Strings in Java | Java

Method Reference Table

Method	Returns	Example	Result
`length()`	number of characters	`"Java".length()`	4
`toUpperCase() / toLowerCase()`	changed case	`"Java".toUpperCase()`	JAVA
`trim() / strip()`	removes outer spaces	`" hi ".trim()`	hi
`substring(b, e)`	part from b to e-1	`"Careeroza".substring(0, 6)`	Career
`contains(s)`	boolean	`"Java".contains("av")`	true
`startsWith / endsWith`	boolean	`"a.pdf".endsWith(".pdf")`	true
`replace(a, b)`	new string	`"a-b-c".replace("-", "/")`	a/b/c
`split(regex)`	String[]	`"a,b,c".split(",")`	[a, b, c]
`isEmpty() / isBlank()`	boolean	`" ".isBlank()`	true
`repeat(n)`	repeated	`"ab".repeat(3)`	ababab

Methods in Action

Example

public class Main {
    public static void main(String[] args) {
        String email = "  [email protected]  ";
        String clean = email.trim().toLowerCase();
        System.out.println("[" + clean + "]");

        int at = clean.indexOf('@');
        String user = clean.substring(0, at);
        String domain = clean.substring(at + 1);
        System.out.println("User: " + user + ", Domain: " + domain);

        System.out.println(clean.contains("@") && clean.endsWith(".com"));
        System.out.println(user.replace(".", " "));

        String[] parts = "Java,Spring,React".split(",");
        System.out.println(parts.length + " skills, first = " + parts[0]);
        System.out.println("=".repeat(20));
        System.out.println("   ".isBlank() + " " + "".isEmpty());
    }
}

Output

[[email protected]]
User: ravi.kumar, Domain: gmail.com
true
ravi kumar
3 skills, first = Java
====================
true true

Practice

Exercise: Given String fullName = "sachin tendulkar"; print the initials in capitals: ST.

Show answer

String[] parts = fullName.split(" ");
String initials = "" + parts[0].charAt(0) + parts[1].charAt(0);
System.out.println(initials.toUpperCase());   // ST