Interpretation of Java documentation: Detailed introduction to the substring() method of the StringBuilder class

Interpretation of Java documentation: Detailed introduction to the substring() method of the StringBuilder class

Introduction:
In Java programming, string processing is a very common operation one. Java provides a series of classes and methods for string processing, among which the StringBuilder class is a commonly used choice for frequent string operations. In the StringBuilder class, the substring() method is a very useful method for intercepting substrings of strings. This article will introduce the substring() method of the StringBuilder class in detail, with specific code examples to help readers better understand and use this method.

Method definition:
First, let’s take a look at the definition of the substring() method:

public String substring(int start)

public String substring(int start, int end)

As can be seen from the above method definition, the substring() method has two overloads The form is used to intercept the substring starting from the specified index to the end of the string, and intercepting the substring within the specified index range.

Method usage:
The two usage methods will be introduced in detail below:

1. substring(int start):
   The function of this method is to intercept the data from the specified index. The substring starting from the end of the string. The specific usage is as follows:

StringBuilder sb = new StringBuilder("Hello World!");
String subString = sb.substring(6); // 截取从索引6开始到末尾的子串
System.out.println(subString);

The above code will output: World!. By passing in index 6, you can intercept the substring starting from index 6 to the end.

2. substring(int start, int end):
   The function of this method is to intercept the substring within the specified index range. The specific usage is as follows:

StringBuilder sb = new StringBuilder("Hello World!");
String subString = sb.substring(0, 5); // 截取从索引0到索引5的子串
System.out.println(subString);

The above code will output: Hello. By passing in the starting index 0 and the ending index 5, you can intercept the substring within the specified index range.

Method return value:
The substring() method returns a new String type object, that is, the intercepted substring. Please note that this method does not modify the original string object.

Exception handling:
When using the substring() method, there are two exceptions that may be thrown to note:

• IndexOutOfBoundsException: If the specified index exceeds the string range.
• NullPointerException: If the StringBuilder object is null.

Therefore, before using the substring() method, exception handling should be performed to ensure the stability and robustness of the program.

Summary:
This article introduces the substring() method of the StringBuilder class in detail and provides specific code examples. By using the substring() method, we can easily intercept the substring of a string. However, you need to pay attention to exception handling during use to avoid runtime exceptions. We hope that the content of this article can help readers better master and apply the substring() method and improve the efficiency and flexibility of string processing.

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