String Concatenation

Joining Strings

Example

Use +, concat(), String.join() or String.format().

public class Main {
    public static void main(String[] args) {
        String first = "Sneha";
        String last = "Reddy";
        System.out.println(first + " " + last);
        System.out.println(first.concat(" ").concat(last));
        System.out.println(String.join(" | ", "Java", "SQL", "Git"));
        System.out.println(String.format("%s %s (%d)", first, last, 24));
        System.out.println("Age: " + 20 + 4);     // text + numbers
        System.out.println(20 + 4 + " is the age"); // numbers first
    }
}

Output

Sneha Reddy
Sneha Reddy
Java | SQL | Git
Sneha Reddy (24)
Age: 204
24 is the age

Note: + works left to right: once a String appears, everything after it is joined as text. 20 + 4 + " x" gives 24 x, but "x " + 20 + 4 gives x 204.

Building Strings in a Loop

Example

Because Strings are immutable, += in a loop creates a new String every time. For many joins use StringBuilder (covered in detail in the medium level).

public class Main {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder();
        for (int i = 1; i <= 5; i++) {
            sb.append(i);
            if (i < 5) sb.append("-");
        }
        System.out.println(sb.toString());
    }
}

Output

1-2-3-4-5