Java StringBuffer offsetByCodePoints()方法及实例

StringBuffer类 的 offsetByCodePoints() 方法返回StringBuffer包含的索引，该索引与作为参数传递的codePointOffset代码点相抵。位于索引和codePointOffset之间的未配对的代用品各算作一个码点。

语法

public int offsetByCodePoints(int index,
                       int codePointOffset)

参数： 该方法需要两个参数。

• index ：要偏移的索引
• codePointOffset ：以代码点为单位的偏移量

返回值 ：该方法返回 该序列中的索引。

异常： 如果以下任何一项为真，该方法会抛出 IndexOutOfBoundsException 。

• index < 0 或 index > 序列的长度。
• codePointOffset > 0并且从index开始的子序列的代码点少于codePointOffset。
• codePointOffset < 并且从index开始的子序列少于codePointOffset代码点的绝对值。

下面的程序演示了StringBuffer类的 offsetByCodePoints()方法。

例1 :

// Java program to demonstrate
// the offsetByCodePoints() Method.
  
class GFG {
    public static void main(String[] args)
    {
  
        // create a StringBuffer object
        // with a String pass as parameter
        StringBuffer
            str
            = new StringBuffer("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

例2 :

// Java program to demonstrate
// the offsetByCodePoints() Method.
  
class GFG {
    public static void main(String[] args)
    {
  
        // create a StringBuffer object
        // with a String pass as parameter
        StringBuffer
            str
            = new StringBuffer("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

例3：演示IndexOutOfBoundException

// Java program to demonstrate
// Exception thrown by offsetByCodePoints() Method.
  
class GFG {
    public static void main(String[] args)
    {
  
        // create a StringBuffer object
        // with a String pass as parameter
        StringBuffer
            str
            = new StringBuffer("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

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