Java StringBuffer subSequence() 方法

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Java StringBuffer subSequence() 方法用于从 StringBuffer 对象中检索子序列。子序列是字符串或序列的一小部分。

subsequence() 方法接受两个整数参数，分别表示开始和结束索引值。如果开始索引或结束索引值为负数，开始索引值大于结束索引值，以及结束索引值大于序列长度，则会抛出异常。

语法

以下是 Java StringBuffer subSequence() 方法的语法：

public CharSequence subSequence(int start, int end)

参数

• start - 这是开始索引，包含在内。
• end - 这是结束索引，不包含在内。

返回值

此方法返回指定的子序列。

示例：获取 StringBuffer 字符串的子序列

如果开始索引和结束索引值为正数且小于序列长度，则 subsequence() 方法会返回给定序列的子序列。

在以下程序中，我们使用“Java Programming”的值实例化StringBuffer 类。然后，使用subsequence() 方法，我们尝试在指定的开始索引 5和结束索引 16处检索给定序列的子序列。

public class SubSequence {
   public static void main(String[] args) {
      //instantiate the StringBuffer class
      StringBuffer sb = new StringBuffer("Java Programming");
      System.out.println("The string is: " + sb.toString());
      //initialize the startIndex and endIndex values
      int startIndex  = 5;
      int endIndex = 16;
      System.out.println("The initialize values of the startIndex and endIndex are: " + startIndex + " and " + endIndex);
      //using the subSequence() method
      System.out.println("The sub-sequence of the given sequence is: " + sb.subSequence(startIndex, endIndex));
   }
}

输出

执行上述程序后，将产生以下结果：

The string is: Java Programming
The initialize values of the startIndex and endIndex are: 5 and 16
The sub-sequence of the given sequence is: Programming

示例：在获取 StringBuffer 字符串的子序列时遇到 StringIndexOutOfBoundsException

如果给定的开始索引和结束索引值为负数，则此方法会抛出StringIndexOutOfBoundsException异常。

在以下程序中，我们使用“Tutorials Point”的值创建一个StringBuffer 类的对象。使用subsequence() 方法，我们尝试在指定的开始索引 -1和结束索引 -2处检索给定序列的子序列。

public class SubSequence {
   public static void main(String[] args) {
      try {
         //create an object of the StringBuffer class
         StringBuffer sb = new StringBuffer("Tutorials Point");
         System.out.println("The string is: " + sb.toString());
         //initialize the startIndex and endIndex values
         int startIndex  = -1;
         int endIndex = -2;
         System.out.println("The initialize values of the startIndex and endIndex are: " + startIndex + " and " + endIndex);
         //using the subSequence() method
         System.out.println("The sub-sequence of the given sequence is: " + sb.subSequence(startIndex, endIndex));
      } catch(IndexOutOfBoundsException e) {
         e.printStackTrace();
         System.out.println("Exception: " + e);
      }
   }
}

输出

以下是上述程序的输出：

The string is: Tutorials Point
The initialize values of the startIndex and endIndex are: -1 and -2
java.lang.StringIndexOutOfBoundsException: Range [-1, -2) out of bounds for length 15
   at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
   at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
   at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
   at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
   at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
   at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckFromToIndex(Preconditions.java:112)
   at java.base/jdk.internal.util.Preconditions.checkFromToIndex(Preconditions.java:349)
   at java.base/java.lang.AbstractStringBuilder.substring(AbstractStringBuilder.java:1057)
   at java.base/java.lang.StringBuffer.subSequence(StringBuffer.java:516)
   at SubSequence.main(SubSequence.java:15)
Exception: java.lang.StringIndexOutOfBoundsException: Range [-1, -2) out of bounds for length 15

示例：在获取 StringBuffer 字符串的子序列时遇到 StringIndexOutOfBoundsException

如果结束索引值大于序列长度，则 subsequence() 方法会抛出StringIndexOutOfBoundsException异常。

在此程序中，我们使用以下值实例化StringBuffer 类

“Hello World”

使用subsequence() 方法，我们尝试在指定的开始索引 5和结束索引 20处检索给定序列的子序列。

public class SubSequence {
   public static void main(String[] args) {
      try {
         //instantiate the StringBuffer class
         StringBuffer sb = new StringBuffer("Hello World");
         System.out.println("The string is: " + sb.toString());
         //initialize the startIndex and endIndex values
         int startIndex  = 2;
         int endIndex = 25;
         System.out.println("The initialize values of the startIndex and endIndex are: " + startIndex + " and " + endIndex);
         //using the subSequence() method
         System.out.println("The sub-sequence of the given sequence is: " + sb.subSequence(startIndex, endIndex));
      } catch(IndexOutOfBoundsException e) {
         e.printStackTrace();
         System.out.println("Exception: " + e);
      }
   }
}

输出

上述程序产生以下结果：

The string is: Hello World
The initialize values of the startIndex and endIndex are: 2 and 25
java.lang.StringIndexOutOfBoundsException: Range [2, 25) out of bounds for length 11
   at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
   at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
   at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
   at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
   at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
   at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckFromToIndex(Preconditions.java:112)
   at java.base/jdk.internal.util.Preconditions.checkFromToIndex(Preconditions.java:349)
   at java.base/java.lang.AbstractStringBuilder.substring(AbstractStringBuilder.java:1057)
   at java.base/java.lang.StringBuffer.subSequence(StringBuffer.java:516)
   at SubSequence.main(SubSequence.java:15)
Exception: java.lang.StringIndexOutOfBoundsException: Range [2, 25) out of bounds for length 11