Java Char Code Get CodePointAt(String str, int index)

Description

Gets the Unicode code point at the given index of the string.

License

Creative Commons License

Parameter

Parameter	Description
str	A string.
index	Index of the current position into the string.

Exception

Parameter	Description
NullPointerException	The parameter str is null.

Return

The Unicode code point at the given position. Returns -1 if index is less than 0, or is the string's length or greater. Returns the replacement character (U + FFFD) if the current character is an unpaired surrogate code point.

Declaration

public static int CodePointAt(String str, int index)

Method Source Code

//package com.java2s;

public class Main {
    /**/*from w w w .  ja  v a2s .  c o  m*/
     * Gets the Unicode code point at the given index of the string.
     * @param str A string.
     * @param index Index of the current position into the string.
     * @return The Unicode code point at the given position. Returns -1 if {@code
     * index} is less than 0, or is the string's length or greater. Returns
     * the replacement character (U + FFFD) if the current character is an
     * unpaired surrogate code point.
     * @throws NullPointerException The parameter {@code str} is null.
     */
    public static int CodePointAt(String str, int index) {
        return CodePointAt(str, index, 0);
    }

    /**
     * Gets the Unicode code point at the given index of the string.
     * @param str A string.
     * @param index Index of the current position into the string.
     * @param surrogateBehavior Specifies what kind of value to return if the
     * previous character is an unpaired surrogate code point: if 0, return
     * the replacement character (U + FFFD); if 1, return the value of the
     * surrogate code point; if neither 0 nor 1, return -1.
     * @return The Unicode code point at the current position. Returns -1 if {@code
     * index} is less than 0, or is the string's length or greater. Returns
     * a value as specified under {@code surrogateBehavior} if the previous
     * character is an unpaired surrogate code point.
     * @throws NullPointerException The parameter {@code str} is null.
     */
    public static int CodePointAt(String str, int index, int surrogateBehavior) {
        if (str == null) {
            throw new NullPointerException("str");
        }
        if (index >= str.length()) {
            return -1;
        }
        if (index < 0) {
            return -1;
        }
        int c = str.charAt(index);
        if ((c & 0xfc00) == 0xd800 && index + 1 < str.length() && str.charAt(index + 1) >= 0xdc00
                && str.charAt(index + 1) <= 0xdfff) {
            // Get the Unicode code point for the surrogate pair
            c = 0x10000 + ((c - 0xd800) << 10) + (str.charAt(index + 1) - 0xdc00);
            ++index;
        } else if ((c & 0xf800) == 0xd800) {
            // unpaired surrogate
            return (surrogateBehavior == 0) ? 0xfffd : ((surrogateBehavior == 1) ? c : (-1));
        }
        return c;
    }
}