Java中的 StringBuilder offsetByCodePoints() 方法及示例

StringBuilder 类的offsetByCodePoints()方法返回 StringBuilder 包含的此字符串中的索引，该索引与 codePointOffset 代码点作为参数传递的索引的偏移量。未配对的代理位于 index 和 codePointOffset 之间，每个都算作一个代码点。

句法：

public int offsetByCodePoints(int index,
                       int codePointOffset)

参数：此方法有两个参数：

• index : 要偏移的索引
• codePointOffset ：代码点的偏移量

返回值：此方法返回此序列中的索引。

异常：如果以下任何一项为真，则此方法抛出IndexOutOfBoundsException ：

• index < 0 或 index > 序列的长度。
• codePointOffset > 0 并且以 index 开头的子序列的代码点少于 codePointOffset
• codePointOffset < 并且 index 之前的子序列小于 codePointOffset 代码点的绝对值。

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

示例 1：

// Java program to demonstrate
// the offsetByCodePoints() 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 index within this sequence
        int returnvalue = str.offsetByCodePoints(1, 4);
  
        // prints the index
        System.out.println("Index = " + returnvalue);
    }
}

输出：

String = WelcomeGeeks
Index = 5

示例 2：

// Java program to demonstrate
// the offsetByCodePoints() Method.
  
class GFG {
    public static void main(String[] args)
    {
  
        // create a StringBuilder object
        // with a String pass as parameter
        StringBuilder
            str
            = new StringBuilder("India Is great");
  
        // print string
        System.out.println("String = " + str.toString());
  
        // returns the index within this sequence
        int returnvalue = str.offsetByCodePoints(2, 9);
  
        // prints the index
        System.out.println("Index = " + returnvalue);
    }
}

输出：

String = India Is great
Index = 11

示例 3：演示 IndexOutOfBoundException

// Java program to demonstrate
// Exception thrown by offsetByCodePoints() Method.
  
class GFG {
    public static void main(String[] args)
    {
  
        // create a StringBuilder object
        // with a String pass as parameter
        StringBuilder
            str
            = new StringBuilder("India");
  
        try {
  
            // returns the index within this sequence
            int returnvalue = str.offsetByCodePoints(2, 9);
  
            // prints the index
            System.out.println("Index = " + returnvalue);
        }
  
        catch (IndexOutOfBoundsException e) {
            System.out.println("Exception: " + e);
        }
    }
}

输出：

Exception: java.lang.IndexOutOfBoundsException

参考：
https://docs.oracle.com/javase/10/docs/api/java Java, int)