Java 中的 StringBuilder codePointAt()示例
原文:https://www . geeksforgeeks . org/stringbuilder-codepointat-in-Java-with-examples/
StringBuilder 类的 codePointAt(int index) 方法以一个索引为参数，在 StringBuilder 包含的 String 中返回该索引处的一个字符 unicode 点，或者我们可以说 charPointAt()方法返回该索引处字符的“unicode 编号”。索引引用字符值(Unicode 代码单位)，索引的值必须介于 0 到长度-1 之间。
如果给定索引处的字符值位于高代理范围内，下一个索引小于该序列的长度，下一个索引处的字符值位于低代理范围内，则返回对应于该代理对的补充代码点。否则，返回给定索引处的字符值。
语法:
public int codePointAt(int index)
参数:该方法接受一个 int 类型参数索引，该索引代表要返回 unicode 值的字符的索引。
返回值:该方法返回指定位置字符的“unicode 数字”。
异常:当索引为负或大于等于长度()时，此方法抛出indexout of boundsexception。
以下程序演示了 StringBuilder 类的 codePointAt()方法:
例 1:
// Java program to demonstrate
// the codePointAt() method
class GFG {
public static void main(String[] args)
{
// create a StringBuilder object
StringBuilder str = new StringBuilder();
// add the String to StringBuilder Object
str.append("Geek");
// get unicode of char at position 1
int unicode = str.codePointAt(1);
// print the result
System.out.println("StringBuilder Object"
+ " contains = " + str);
System.out.println("Unicode of Character"
+ " at Position 1 "
+ "in StringBuilder = "
+ unicode);
// get unicode of char at position 3
unicode = str.codePointAt(3);
// print the result
System.out.println("Unicode of Character "
+ "at Position 3 "
+ "in StringBuilder = "
+ unicode);
}
}
Output:
StringBuilder Object contains = Geek
Unicode of Character at Position 1 in StringBuilder = 101
Unicode of Character at Position 3 in StringBuilder = 107
例 2:
// Java program to demonstrate
// the codePointAt() 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 is " + str.toString());
// loop through string and print every Character
for (int i = 0; i < str.length(); i++) {
// get char at position i
char ch = str.charAt(i);
// get unicode of char at position i
int unicode = str.codePointAt(i);
// print char and Unicode
System.out.println("Unicode of Char " + ch
+ " at position " + i
+ " is " + unicode);
}
}
}
Output:
String is WelcomeGeeks
Unicode of Char W at position 0 is 87
Unicode of Char e at position 1 is 101
Unicode of Char l at position 2 is 108
Unicode of Char c at position 3 is 99
Unicode of Char o at position 4 is 111
Unicode of Char m at position 5 is 109
Unicode of Char e at position 6 is 101
Unicode of Char G at position 7 is 71
Unicode of Char e at position 8 is 101
Unicode of Char e at position 9 is 101
Unicode of Char k at position 10 is 107
Unicode of Char s at position 11 is 115
示例 3: 演示 IndexOutOfBoundsException
// Java program demonstrate
// IndexOutOfBoundsException thrown by
// the codePointAt() Method.
class GFG {
public static void main(String[] args)
{
// create a StringBuilder object
// with a String pass as parameter
StringBuilder
str
= new StringBuilder("WelcomeGeeks");
try {
// get char at position out of range of index
int i = str.codePointAt(str.length());
}
catch (IndexOutOfBoundsException e) {
System.out.println("Exception: " + e);
}
}
}
Output:
Exception: java.lang.StringIndexOutOfBoundsException:
String index out of range: 12
参考: https://docs . Oracle . com/javae/10/docs/API/Java/lang/string builder . html # code point(int)
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