How to truncate a string

Short answer

Take the start of the string with substring(), limiting the length with Math.min():

void main() {
    String text = "Hello, World";
    IO.println(text.substring(0, Math.min(text.length(), 5)));
}

Output:

Hello

With an ellipsis

Add an ellipsis only if the string is actually longer than the limit:

String truncate(String text, int max) {
    return text.length() <= max ? text : text.substring(0, max - 1) + "…";
}
 
void main() {
    IO.println(truncate("A very long title", 10));
    IO.println(truncate("Short", 10));
}

Output:

A very lo…
Short

At a word boundary

To avoid cutting a word in half, find the last space before the limit:

String truncateWords(String text, int max) {
    if (text.length() <= max) {
        return text;
    }
    int space = text.lastIndexOf(' ', max);
    return (space > 0 ? text.substring(0, space) : text.substring(0, max)) + "…";
}
 
void main() {
    IO.println(truncateWords("Learn Java step by step", 12));
}

Output:

Learn Java…

Common mistake

Calling substring(0, max) on a string shorter than the limit:

void main() {
    String text = "Hi";
    IO.println(text.substring(0, 5));
}

Output:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: Range [0, 5) out of bounds for length 2

Limit the end with Math.min(text.length(), max).

Thanks for reading!

Short answer

With an ellipsis

At a word boundary

Common mistake

Functions used in this recipe

Thanks for reading!