StringBuilder类的charAt(int index)方法用于返回StringBuilder Object包含的String的指定索引处的字符。索引值应介于0和length()-1之间。
用法:
public char charAt(int index)
参数:此方法接受一个int类型参数索引,该索引表示要返回的字符的索引。
返回值:此方法在指定位置返回字符。
异常:当index为负或大于或等于length()时,此方法将引发IndexOutOfBoundsException。
下面的程序演示StringBuilder类的charAt()方法:
示例1:
// Java program to demonstrate
// the charAt() 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 char at position 1
char ch = str.charAt(1);
// print the result
System.out.println("StringBuilder Object"
+ " contains = " + str);
System.out.println("Character at Position 1"
+ " in StringBuilder = " + ch);
}
}
输出:
StringBuilder Object contains = Geek Character at Position 1 in StringBuilder = e
示例2:
// Java program demonstrate
// the charAt() 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);
// print char
System.out.println("Char at position "
+ i + " is " + ch);
}
}
}
输出:
String is WelcomeGeeks Char at position 0 is W Char at position 1 is e Char at position 2 is l Char at position 3 is c Char at position 4 is o Char at position 5 is m Char at position 6 is e Char at position 7 is G Char at position 8 is e Char at position 9 is e Char at position 10 is k Char at position 11 is s
示例3:演示IndexOutOfBoundException
// Java program to demonstrate
// IndexOutOfBound exception thrown by the charAt() Method.
class GFG {
public static void main(String[] args)
{
try {
// create a StringBuilder object
// with a String pass as parameter
StringBuilder
str
= new StringBuilder("WelcomeGeeks");
// get char at position i
char ch = str.charAt(str.length());
// print char
System.out.println("Char at position "
+ str.length() + " is "
+ ch);
}
catch (Exception e) {
System.out.println("Exception: " + e);
}
}
}
输出:
Exception: java.lang.StringIndexOutOfBoundsException: String index out of range: 12
参考:
https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuilder.html#charAt(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 charAt() 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。