如何在修剪后的字符串上添加“…”？

Question

I've set the maxLength of the string to 100, so I need that the first 97 characters are normal chars, but the last three have to be "...".

Tried to add +"..." to the string, but, naturally, when it reaches the limit, nothing can be added there.

How to fix this?

Thanks!

Answer 1

You haven't mentioned why are you trimming the String. If you are trimming it to use it in TextView/Button/etc, don't forget you can use maxLines and ellipsize to achieve desired effect.

<TextView
    android:id="@+id/myText"
    android:maxLines="1"
    android:ellipsize="end"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"/>

(If I am wrong and this has nothing to do with TextViews, just ignore this answer :))

Answer 2

A solution that copes with strings of all length:

String trim(String string, int maxLength)
{
    if (maxLength < 3)
        throw new IllegalArgumentException("Max length (" + maxLength + ") must at least 3");

    return string.length() > maxLength ? 
               string.substring(0, maxLength - 3) + "..." : 
               string;
}

Answer 3

Use String#substring as follows:

int maxLength = 100;
String lastThree = "...";
return str.substring(0, maxLength - lastThree.length()) + "...");

A working example:

public class Test {
    static final String str = "redgreenblue";
    static final String t = "...";
    public static void main(String[] args) {
        try {
            System.out.println(str.substring(0,10-t.length()) + t);
        }
        catch (StringIndexOutOfBoundsException e) {
            System.out.println(str + t);
        }
    }
}

Answer 4

You should almost always use a StringBuilder when putting a string together. In this case, you can call setCharAt() to change the last three characters. If you really really do need to use a String directly, use substring() to capture the first 97 characters and then add the ellipsis.