Java StringBuilder codePointCount()方法及示例

StringBuilder类 的 codePointBefore() 方法返回StringBuilder包含的String中指定文本范围内的Unicode代码点的数量。该方法需要两个索引作为参数–第一个是beginIndex，代表文本范围的第一个字符的索引，第二个是endIndex，代表文本范围的最后一个字符之后的索引。索引指的是char值（Unicode代码单位），索引的值必须在0到length-1之间。文本范围从beginIndex开始，延伸到endIndex-1的字符。因此，文本范围的长度（以字符为单位）为 endIndex-beginIndex。

语法

public int     codePointCount(int beginIndex, int endIndex)

参数： 该方法接受两个参数

返回值： 该方法返回 指定文本范围内的Unicode代码点的数量 。

异常： 如果出现以下情况，该方法会抛出 IndexOutOfBoundsException 。

以下程序演示了StringBuilder类的codePointCount()方法。

例1:

// Java program to demonstrate// the codePointCount() Method.  class GFG {    public static void main(String[] args)    {          // create a StringBuilder object        // with a String pass as parameter        StringBuilder            str            = new StringBuilder("WelcomeGeeks");          // print string        System.out.println("String = " + str.toString());          // returns the codepoint count from index 2 to 8        int codepoints = str.codePointCount(2, 8);        System.out.println("No of Unicode code points = "                           + codepoints);    }}

输出:

String = WelcomeGeeksNo of Unicode code points = 6

例2:

// Java program to demonstrate// the codePointCount() Method.  class GFG {    public static void main(String[] args)    {        // create a StringBuilder object        // with a String pass as parameter        StringBuilder            str            = new StringBuilder("GeeksForGeeks");          // print string        System.out.println("String = "                           + str.toString());          // returns the codepoint count        // from index 3 to 7        int            codepoints            = str.codePointCount(3, 7);        System.out.println("No of Unicode code points"                           + " between index 3 and 7 = "                           + codepoints);    }}

输出:

String = GeeksForGeeksNo of Unicode code points between index 3 and 7 = 4

例3：演示IndexOutOfBoundsException

// Java program to demonstrate// exception thrown by the codePointCount() Method.  class GFG {    public static void main(String[] args)    {          // create a StringBuilder object        // with a String pass as parameter        StringBuilder            str            = new StringBuilder("GeeksForGeeks");          try {              // make beginIndex greater than endIndex            int codepoints = str.codePointCount(7, 4);        }          catch (Exception e) {            System.out.println("Exception: " + e);        }    }}

输出:

Exception: java.lang.IndexOutOfBoundsException

参考资料：
https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuilder.html#codePointCount(int, int)。