从字符串中获取字符的 Java 程序

原文:https://www . geesforgeks . org/Java-program-to-get-a-character-from-string/

给定一个字符串，任务是在特定的索引处从该字符串中获取特定的字符。

示例:

Input: str = "Geeks", index = 2
Output: e

Input: str = "GeeksForGeeks", index = 5
Output: F

以下是各种方法:

• Using String.charAt() method:

  1. 获取字符串和索引
  2. 使用 String.charAt(index)方法获取特定字符。
  3. 返回特定字符。

  下面是上述方法的实现:

  ```java // Java program to get a specific character // from a given String at a specific index

  class GFG {

  // Function to get the specific character     public static char     getCharFromString(String str, int index)     {         return str.charAt(index);     }

  // Driver code     public static void main(String[] args)     {

  // Get the String         String str = "GeeksForGeeks";

  // Get the index         int index = 5;

  // Get the specific character         char ch = getCharFromString(str, index);

  System.out.println("Character from " + str                            + " at index " + index                            + " is " + ch);     } } ```

  Output:

  ```java Character from GeeksForGeeks at index 5 is F

  ```

• Using String.toCharArray() method:

  1. 获取字符串和索引
  2. 使用 String.toCharArray()方法将字符串转换为字符数组。
  3. 获取字符数组特定索引处的特定字符。
  4. 返回特定字符。

  下面是上述方法的实现:

  ```java // Java program to get a specific character // from a given String at a specific index

  class GFG {

  // Function to get the specific character     public static char     getCharFromString(String str, int index)     {         return str.toCharArray()[index];     }

  // Driver code     public static void main(String[] args)     {         // Get the String         String str = "GeeksForGeeks";

  // Get the index         int index = 5;

  // Get the specific character         char ch = getCharFromString(str, index);

  System.out.println("Character from " + str                            + " at index " + index                            + " is " + ch);     } } ```

  Output:

  ```java Character from GeeksForGeeks at index 5 is F

  ```

• Using Java 8 Streams:

  1. 获取字符串和索引
  2. 使用 String.chars()方法将字符串转换为 IntStream。
  3. 使用 IntStream.mapToObj()方法将 IntStream 转换为 Stream 。
  4. 使用 toArray()方法将流转换为字符【】。
  5. 从这个字符数组中获取特定索引处的元素。
  6. 返回具体人物。

  下面是上述方法的实现:

  ```java // Java program to get a specific character // from a given String at a specific index

  class GFG {

  // Function to get the specific character     public static char     getCharFromString(String str, int index)     {         return str             // Convert String into IntStream             .chars()

  // Convert IntStream into Stream             .mapToObj(ch -> (char)ch)

  // Convert Stream into Character[]             // and get the element at the specific index             .toArray(Character[] ::new)[index];     }

  // Driver code     public static void main(String[] args)     {         // Get the String         String str = "GeeksForGeeks";

  // Get the index         int index = 5;

  // Get the specific character         char ch = getCharFromString(str, index);

  System.out.println("Character from " + str                            + " at index " + index                            + " is " + ch);     } } ```

  Output:

  ```java Character from GeeksForGeeks at index 5 is F

  ```

• Using String.codePointAt() method:

  1. 获取字符串和索引
  2. 使用 String.codePointAt()方法获取特定索引处的特定字符 ASCII 值。
  3. 使用类型转换将该 ASCII 值转换为字符。
  4. 返回特定字符。

  下面是上述方法的实现:

  ```java // Java program to get a specific character // from a given String at a specific index

  class GFG {

  // Function to get the specific character     public static char     getCharFromString(String str, int index)     {         return (char)str.codePointAt(index);     }

  // Driver code     public static void main(String[] args)     {         // Get the String         String str = "GeeksForGeeks";

  // Get the index         int index = 5;

  // Get the specific character         char ch = getCharFromString(str, index);

  System.out.println("Character from " + str                            + " at index " + index                            + " is " + ch);     } } ```

  Output:

  ```java Character from GeeksForGeeks at index 5 is F

  ```

• Using String.getChars() method:

  1. 获取字符串和索引
  2. 创建一个大小为 1 的空字符数组
  3. 使用 String.getChars()方法将字符串中特定索引处的元素复制到 char[]中。
  4. 获取字符数组索引 0 处的特定字符。
  5. 返回特定字符。

  下面是上述方法的实现:

  ```java // Java program to get a specific character // from a given String at a specific index

  class GFG {

  // Function to get the specific character     public static char     getCharFromString(String str, int index)     {         // Create a character array of size 1         char[] singleCharArray = new char[1];

  // Get the specific character from the String         // into the char[] at index 0         str.getChars(index, index + 1, singleCharArray, 0);

  // Return the specific character         // present at index 0 in char[]         return singleCharArray[0];     }

  // Driver code     public static void main(String[] args)     {         // Get the String         String str = "GeeksForGeeks";

  // Get the index         int index = 5;

  // Get the specific character         char ch = getCharFromString(str, index);

  System.out.println("Character from " + str                            + " at index " + index                            + " is " + ch);     } } ```

  Output:

  ```java Character from GeeksForGeeks at index 5 is F

  ```

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