Java StringBuilder subSequence()方法及示例

StringBuilder类的 subSequence(int start, int end) 方法是一个内置的方法，用于 返回 位于该序列的索引开始和结束-1之间的 字符的子序列 。该子序列以索引开始处的字符值开始，以（end-1）处的字符值结束。返回的子序列的长度是end-start。因此，如果start等于end，那么将返回一个空的子序列。

语法

public CharSequence subSequence?(int start, int end)

参数：

该方法接受两个参数。

start 是整数类型的值，指的是子序列的起始索引。end 是整数类型的值，指的是子序列的最后索引。

返回：

该方法返回start到end-1范围内的指定子序列。

异常：

如果start或end为负数，如果end大于length()，或者start大于end，则抛出 IndexOutOfBoundsException 。

以下程序说明了java.lang.StringBuilder.subSequence()方法：

示例1 :

// Java program to demonstrate// the subSequence() 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("String contains = " + str);         // get subSequence between index 0 to 7        // using subSequence() and print        System.out.println("SubSequence = "                           + str.subSequence(0, 7));    }}

输出

String length = 12 and contains = WelcomeGeeksSubSequence = Welcome

例2 :

// Java program to demonstrate// the subSequence() Method. class GFG {     public static void main(String[] args)    {        // create a StringBuilder object        // with a String pass as parameter        StringBuilder str            = new StringBuilder("Indian Team Played Well");         // print string        System.out.println("String contains = " + str);         // get subSequence between index 0 to 7        // using subSequence() and print        System.out.println("SubSequence = "                           + str.subSequence(7, 18));    }}

输出

String contains = Indian Team Played WellSubSequence = Team Played

例3： 当开始>结束。

// Java program to demonstrate// Exception thrown by the subSequence() Method. class GFG {     public static void main(String[] args)    {        // create a StringBuilder object        // with a String pass as parameter        StringBuilder str            = new StringBuilder("Indian Team Played Well");         try {            // get subSequence between index 0 to 7            // using subSequence() and print            System.out.println(str.subSequence(19, 18));        }        catch (Exception e) {            e.printStackTrace();        }    }}

输出

java.lang.StringIndexOutOfBoundsException: String index out of range: -1    at java.lang.AbstractStringBuilder.substring(AbstractStringBuilder.java:935)    at java.lang.StringBuilder.substring(StringBuilder.java:76)    at java.lang.AbstractStringBuilder.subSequence(AbstractStringBuilder.java:912)    at java.lang.StringBuilder.subSequence(StringBuilder.java:76)    at GFG.main(File.java:16)

参考文献：
https://docs.oracle.com/javase/10/docs/api/java/lang/StringBuilder.html#subSequence(int, int)