Java程序从字符串中获取一个字符

给定一个字符串 str，任务是从该字符串的特定索引处获取特定字符。

例子：

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

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

以下是执行此操作的各种方法：

• 使用 String.charAt() 方法：
  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 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);
      }
  }
  

  输出：

  Character from GeeksForGeeks at index 5 is F
  

• 使用 String.toCharArray() 方法：
  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 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);
      }
  }
  

  输出：

  Character from GeeksForGeeks at index 5 is F
  

• 使用Java 8 流：
  1. 获取字符串和索引
  2. 使用 String.chars() 方法将 String 转换为 IntStream。
  3. 将 IntStream 转换为 Stream使用 IntStream.mapToObj() 方法。
  4. 转换流使用 toArray() 方法进入字符[]。
  5. 从此字符数组中获取特定索引处的元素。
  6. 返回特定字符。

  下面是上述方法的实现：

  // 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);
      }
  }
  

  输出：

  Character from GeeksForGeeks at index 5 is F
  

• 使用 String.codePointAt() 方法：
  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. 使用类型转换将此 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 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);
      }
  }
  

  输出：

  Character from GeeksForGeeks at index 5 is F
  

• 使用 String.getChars() 方法：
  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() 方法将特定索引处的元素从 String 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 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);
      }
  }
  

  输出：

  Character from GeeksForGeeks at index 5 is F