Java StringBuilder codePointCount()用法及代码示例

StringBuilder类的codePointBefore()方法返回StringBuilder包含的String中指定文本范围内的Unicode代码点数。此方法采用两个索引作为参数：first beginIndex表示文本范围的第一个字符的索引，endIndex表示文本范围的最后一个字符的索引。索引引用char值(Unicode代码单位)，并且索引的值必须介于0到length-1之间。文本范围从beginIndex开始，并扩展到索引endIndex – 1处的char。因此，文本范围的长度(以char为单位)为endIndex-beginIndex。

用法:

public int 
    codePointCount(int beginIndex, int endIndex)

参数：该方法接受两个参数

beginIndex:文本范围的第一个字符的索引。
endIndex:文本范围的最后一个字符之后的索引。

返回值：此方法返回指定文本范围内的Unicode代码点数。

异常：在以下情况下，此方法将引发IndexOutOfBoundsException：

beginIndex小于零，
或endIndex大于String的长度，
或beginIndex大于endIndex。

下面的程序演示StringBuilder类的codePointCount()方法：

示例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 = WelcomeGeeks
No of Unicode code points = 6

示例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 = GeeksForGeeks
No of Unicode code points between index 3 and 7 = 4

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

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注：本文由纯净天空筛选整理自AmanSingh2210大神的英文原创作品 StringBuilder codePointCount() in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。