Converts the specified character (Unicode code point) to its UTF-16 representation. - Java java.lang

Java examples for java.lang:String Unicode

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Description

Converts the specified character (Unicode code point) to its UTF-16 representation.

Demo Code


//package com.java2s;

public class Main {
    public static void main(String[] argv) throws Exception {
        int codePoint = 2;
        System.out.println(java.util.Arrays.toString(toChars(codePoint)));
    }//from w  w w  . java2 s.c  o m

    /**
     * The minimum value of a Unicode high-surrogate code unit in the
     * UTF-16 encoding. A high-surrogate is also known as a
     * <i>leading-surrogate</i>.
     *
     * @since 1.5
     */
    public static final char MIN_HIGH_SURROGATE = '\uD800';
    /**
     * The minimum value of a Unicode low-surrogate code unit in the
     * UTF-16 encoding. A low-surrogate is also known as a
     * <i>trailing-surrogate</i>.
     *
     * @since 1.5
     */
    public static final char MIN_LOW_SURROGATE = '\uDC00';
    /**
     * The minimum value of a supplementary code point.
     *
     * @since 1.5
     */
    public static final int MIN_SUPPLEMENTARY_CODE_POINT = 0x010000;
    /**
     * The maximum value of a Unicode code point.
     *
     * @since 1.5
     */
    public static final int MAX_CODE_POINT = 0x10ffff;

    /**
     * Converts the specified character (Unicode code point) to its
     * UTF-16 representation. If the specified code point is a BMP
     * (Basic Multilingual Plane or Plane 0) value, the same value is
     * stored in <code>dst[dstIndex]</code>, and 1 is returned. If the
     * specified code point is a supplementary character, its
     * surrogate values are stored in <code>dst[dstIndex]</code>
     * (high-surrogate) and <code>dst[dstIndex+1]</code>
     * (low-surrogate), and 2 is returned.
     *
     * @param  codePoint the character (Unicode code point) to be converted.
     * @param  dst an array of <code>char</code> in which the
     * <code>codePoint</code>'s UTF-16 value is stored.
     * @param dstIndex the start index into the <code>dst</code>
     * array where the converted value is stored.
     * @return 1 if the code point is a BMP code point, 2 if the
     * code point is a supplementary code point.
     * @exception IllegalArgumentException if the specified
     * <code>codePoint</code> is not a valid Unicode code point.
     * @exception NullPointerException if the specified <code>dst</code> is null.
     * @exception IndexOutOfBoundsException if <code>dstIndex</code>
     * is negative or not less than <code>dst.length</code>, or if
     * <code>dst</code> at <code>dstIndex</code> doesn't have enough
     * array element(s) to store the resulting <code>char</code>
     * value(s). (If <code>dstIndex</code> is equal to
     * <code>dst.length-1</code> and the specified
     * <code>codePoint</code> is a supplementary character, the
     * high-surrogate value is not stored in
     * <code>dst[dstIndex]</code>.)
     * @since  1.5
     */
    public static int toChars(int codePoint, char[] dst, int dstIndex) {
        if (codePoint < 0 || codePoint > MAX_CODE_POINT) {
            throw new IllegalArgumentException();
        }
        if (codePoint < MIN_SUPPLEMENTARY_CODE_POINT) {
            dst[dstIndex] = (char) codePoint;
            return 1;
        }
        toSurrogates(codePoint, dst, dstIndex);
        return 2;
    }

    /**
     * Converts the specified character (Unicode code point) to its
     * UTF-16 representation stored in a <code>char</code> array. If
     * the specified code point is a BMP (Basic Multilingual Plane or
     * Plane 0) value, the resulting <code>char</code> array has
     * the same value as <code>codePoint</code>. If the specified code
     * point is a supplementary code point, the resulting
     * <code>char</code> array has the corresponding surrogate pair.
     *
     * @param  codePoint a Unicode code point
     * @return a <code>char</code> array having
     *         <code>codePoint</code>'s UTF-16 representation.
     * @exception IllegalArgumentException if the specified
     * <code>codePoint</code> is not a valid Unicode code point.
     * @since  1.5
     */
    public static char[] toChars(int codePoint) {
        if (codePoint < 0 || codePoint > MAX_CODE_POINT) {
            throw new IllegalArgumentException();
        }
        if (codePoint < MIN_SUPPLEMENTARY_CODE_POINT) {
            return new char[] { (char) codePoint };
        }
        char[] result = new char[2];
        toSurrogates(codePoint, result, 0);
        return result;
    }

    static void toSurrogates(int codePoint, char[] dst, int index) {
        int offset = codePoint - MIN_SUPPLEMENTARY_CODE_POINT;
        dst[index + 1] = (char) ((offset & 0x3ff) + MIN_LOW_SURROGATE);
        dst[index] = (char) ((offset >>> 10) + MIN_HIGH_SURROGATE);
    }
}

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