Java StringBuilder deleteCharAt()方法及实例

StringBuilder类 的 deleteCharAt(int index) 方法从StringBuilder包含的字符串中删除给定索引处的字符。该方法将index作为参数，代表我们要删除的字符的索引，并将剩余的字符串作为StringBuilder对象返回。使用该方法后，这个StringBuilder缩短了一个字符。 语法

public StringBuilder deleteCharAt(int index)

参数： 该方法接受一个参数 index ，代表你要删除的字符的索引。
返回值： 该方法在删除字符后返回 这个StringBuilder对象 。
异常： 如果索引小于0，或者索引大于String的长度，该方法会抛出 StringIndexOutOfBoundsException 。下面的程序演示了StringBuilder类的deleteCharAt()方法：

例1 :

// Java program to demonstrate// the deleteCharAt() 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("Before removal String = "                           + str.toString());         // remove the Character from index 8        StringBuilder afterRemoval = str.deleteCharAt(8);         // print string after removal of Character        System.out.println("After removal of character"                           + " at index 8 = "                           + afterRemoval.toString());    }}

输出

Before removal String = WelcomeGeeksAfter removal of character at index 8 = WelcomeGeks

例2 :

// Java program to demonstrate// the deleteCharAt() Method. class GFG {    public static void main(String[] args)    {         // create a StringBuilder object        // with a String pass as parameter        StringBuilder            str            = new StringBuilder("GeeksforGeeks");         // print string        System.out.println("Before removal String = "                           + str.toString());         // remove the Character from index 3        str = str.deleteCharAt(3);         // print string after removal of Character        System.out.println("After removal of Character"                           + " from index=3"                           + " String becomes => "                           + str.toString());         // remove the substring from index 5        str = str.deleteCharAt(5);         // print string after removal of Character        System.out.println("After removal of Character"                           + " from index=5"                           + " String becomes => "                           + str.toString());    }}

输出

Before removal String = GeeksforGeeksAfter removal of Character from index=3 String becomes => GeesforGeeksAfter removal of Character from index=5 String becomes => GeesfrGeeks

例3： 演示IndexOutOfBoundException

// Java program to demonstrate// exception thrown by the deleteCharAt() Method. class GFG {    public static void main(String[] args)    {         // create a StringBuilder object        // with a String pass as parameter        StringBuilder            str            = new StringBuilder("evil dead_01");         try {             // make index > length of String            StringBuilder                afterRemoval                = str.deleteCharAt(14);        }         catch (Exception e) {            System.out.println("Exception: " + e);        }    }}

输出

Exception: java.lang.StringIndexOutOfBoundsException: String index out of range: 14

**参考资料: ** https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuilder.html#deleteCharAt(int)