Detailed explanation of the use of two methods in regular and object in Java

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Regular expression: "." and "\"

"." are expressed in regular expressions represents any character in the formula.

"\" is an escape character in regular expressions. When we need to describe a special character that has been used by a regular expression, we can use "\" to convert it into its original meaning. .

"\" also has some predefined special contents in regular expressions:

\d: represents any number

\w: represents any word character ( Can only be numbers, letters, and underscores)

\s: Represents any blank character (\t \r \n \f \x0B)

\D: Represents any non-numeric character

\W: Represents any non-word character

\S: Represents any non-whitespace character

"Character set []" is used to describe a single character, square brackets The content of this character can be defined internally, and a range can also be described. For example: [abc]: means that the character can only be a or b or c

[123]: means that the character can only be 1 or 2 or 3. When we need to describe all lowercase letters, we can use range [a-z], indicating that the character can be any lowercase letter.

You can also use [0-9] to indicate that the character can be any number.

You can also select from multiple ranges. For example, [a-zA-Z0-9_] means that the character can be any letter, number and "underscore".

"+": Indicates that the content can appear at least 1 time in a row

"*": Indicates that the content appears 0-several times

"?": Indicates that the content appears 0 times -1 times

{n}: Indicates that the content must appear n times

{n,m}: Indicates that the content appears n-m times

{n,}: Indicates that the content appears At least n times

() can treat the content as a whole, and "|" can be used in () to express or relationships.

Add "^" at the beginning and "$" at the end of the regular expression to represent a whole, but the default matching whole is used in Java.

1.1 One of the related methods of string support for regular expressions

boolean matches(String regec)

Use the given regular expression to match the format of the current string Whether it meets the requirements of the regular expression, true, the regular expression passed in by the macthes method provided by String is a full match even without adding boundary characters

1.2 String supports regular expressions Expression method two:

String[] solit(String regex)

Split the content of the current string according to the parts that satisfy the regular expression, store the split strings into an array and return

If it is found that the split part is continuously matched during the splitting process, an empty string will be removed in the middle. However, if there is a continuous match at the end of the string, the splitting of the empty string will be ignored

1.3 The third regular expression method supported by String

String replaceAll(String regex,String str)

Replace the part of the current string that satisfies the regular expression with the given String

2.1 Principles of overriding the tostring method of object

Normally, when we need to use the toString method of an object, This method should be rewritten, because the method provided by object returns the handle of the object: class name@address, so that the actual relevant information about the beauty of the object cannot be obtained.

The string returned by tostring should contain The specific format content of the current object's content (attribute value) is determined according to the actual design requirements of the current class

2.2 equals method of object

equals method The design purpose is to compare whether the contents of two objects are consistent

Comparison principle: comparing the attribute values ​​​​of two objects does not necessarily require that the attribute values ​​​​are the same, depending on the design requirements of the current class.

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