Java StringBuffer subSequence() 方法

---

---

Java StringBuffer subSequence() 方法用於從 StringBuffer 物件中檢索子序列。子序列是字串或序列的一小部分。

subsequence() 方法接受兩個整數引數，分別表示開始和結束索引值。如果開始索引或結束索引值為負數，開始索引值大於結束索引值，以及結束索引值大於序列長度，則會丟擲異常。

語法

以下是 Java StringBuffer subSequence() 方法的語法：

public CharSequence subSequence(int start, int end)

引數

• start - 這是開始索引，包含在內。
• end - 這是結束索引，不包含在內。

返回值

此方法返回指定的子序列。

示例：獲取 StringBuffer 字串的子序列

如果開始索引和結束索引值為正數且小於序列長度，則 subsequence() 方法會返回給定序列的子序列。

在以下程式中，我們使用“Java Programming”的值例項化StringBuffer 類。然後，使用subsequence() 方法，我們嘗試在指定的開始索引 5和結束索引 16處檢索給定序列的子序列。

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));
   }
}

輸出

執行上述程式後，將產生以下結果：

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：在獲取 StringBuffer 字串的子序列時遇到 StringIndexOutOfBoundsException

如果給定的開始索引和結束索引值為負數，則此方法會丟擲StringIndexOutOfBoundsException異常。

在以下程式中，我們使用“Tutorials Point”的值建立一個StringBuffer 類的物件。使用subsequence() 方法，我們嘗試在指定的開始索引 -1和結束索引 -2處檢索給定序列的子序列。

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);
      }
   }
}

輸出

以下是上述程式的輸出：

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：在獲取 StringBuffer 字串的子序列時遇到 StringIndexOutOfBoundsException

如果結束索引值大於序列長度，則 subsequence() 方法會丟擲StringIndexOutOfBoundsException異常。

在此程式中，我們使用以下值例項化StringBuffer 類

“Hello World”

使用subsequence() 方法，我們嘗試在指定的開始索引 5和結束索引 20處檢索給定序列的子序列。

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);
      }
   }
}

輸出

上述程式產生以下結果：

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