Useful String Methods

Beyond the Basics

Method	Example	Result
`split`	`"a,b,c".split(",")`	`[a, b, c]`
`String.join`	`String.join("-", "a", "b")`	`a-b`
`strip` / `isBlank`	`" hi ".strip()`	`hi`
`repeat`	`"ab".repeat(3)`	`ababab`
`String.format` / `formatted`	`"%05d".formatted(42)`	`00042`
`chars`	`"aab".chars().filter(c -> c == 'a').count()`	`2`
`compareTo`	`"apple".compareTo("banana")`	negative

Examples

Example

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        String csv = "Asha,Ravi,,Meena";
        String[] parts = csv.split(",");
        System.out.println(Arrays.toString(parts) + " (" + parts.length + " parts)");
        System.out.println(String.join(" | ", parts));

        String input = "   Hello Java   ";
        System.out.println("[" + input.strip() + "]");
        System.out.println("blank? " + "   ".isBlank());

        System.out.println("=".repeat(20));
        System.out.println(String.format("%-8s|%6.2f|%04d", "Tea", 12.5, 7));
        System.out.println("Invoice %s for Rs %,d".formatted("INV-9", 1250000));

        String word = "banana";
        long aCount = word.chars().filter(c -> c == 'a').count();
        System.out.println("a appears " + aCount + " times");
        System.out.println("apple vs banana: " + "apple".compareTo("banana"));
        System.out.println("contains 'nan': " + word.contains("nan"));
    }
}

Output

[Asha, Ravi, , Meena] (4 parts)
Asha | Ravi |  | Meena
[Hello Java]
blank? true
====================
Tea     | 12.50|0007
Invoice INV-9 for Rs 1,250,000
a appears 3 times
apple vs banana: -1
contains 'nan': true

Practice

Exercise: Write a method String initials(String fullName) that returns "S.R.T." for "sachin ramesh tendulkar". Use split and StringBuilder.

Show answer

static String initials(String fullName) {
    StringBuilder sb = new StringBuilder();
    for (String part : fullName.strip().split(" ")) {
        if (!part.isEmpty()) {
            sb.append(Character.toUpperCase(part.charAt(0))).append('.');
        }
    }
    return sb.toString();
}