StringBuffer类的codePointBefore()方法是用于将索引作为参数并返回该索引之前存在的字符的“Unicode number”的方法。 index的值必须介于0到length-1之间。
如果(index-1)处的char值在低代理范围内,(index-2)处的char不为负且值在高代理范围内,则返回代理对的补充代码点值通过方法。如果索引-1处的char值是未配对的低代理或高代理,则返回代理值。
用法:
public int codePointBefore(int index)
参数:此方法采用一个参数索引,该参数索引是要返回其unicode值的字符之后的字符的索引。
返回值:此方法返回给定索引之前字符的unicode号。
异常:当index为负或大于或等于length()时,此方法将引发IndexOutOfBoundsException。
以下示例程序旨在说明codePointBefore()方法:
范例1:
// Java program to demonstrate
// the codePointBefore() Method.
class GFG {
public static void main(String[] args)
{
// create a StringBuffer object
// with a String pass as parameter
StringBuffer
str
= new StringBuffer("GeeksForGeeks Contribute");
// get unicode of char at index 13
// using codePointBefore() method
int unicode = str.codePointBefore(14);
// print char and Unicode
System.out.println("Unicode of character"
+ " at position 13 = "
+ unicode);
}
}
输出:
Unicode of character at position 13 = 32
范例2:演示IndexOutOfBoundsException
// Java program to demonstrate
// exception thrown by codePointBefore() Method.
class GFG {
public static void main(String[] args)
{
// create a StringBuffer object
// with a String pass as parameter
StringBuffer
str
= new StringBuffer("GEEKSFORGEEKS");
try {
// get unicode of char at position 22
int unicode = str.codePointBefore(22);
}
catch (Exception e) {
System.out.println("Exception:" + e);
}
}
}
输出:
Exception:java.lang.StringIndexOutOfBoundsException: String index out of range:22
参考文献:
https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuffer.html#codePointBefore(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 StringBuffer codePointBefore() method 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。