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Java determines whether a string is a date

How to determine whether a string is a date in Java: first specify the date format, and then use the DateFormat class or SimpleDateFormat class to determine whether it is the correct date format and whether it is a date.

Nov 21, 2019 pm 02:53 PM

java

How to determine whether a string is in json format in java

The method to determine whether a string is in json format in Java is: first format the string that needs to be processed, and then use the methods "startsWith()" and "endsWith()" to determine whether the first and last letters of the string are "{}" or "[]", if neither, it is not in json format.

Nov 21, 2019 pm 02:44 PM

java json judgment string Format

What collections are there in java

There are three main types of collections in Java: set, list and map. List: stores ordered and repeatable elements, set: stores unordered and non-repeatable elements, map: stores elements in key-value form.

Nov 21, 2019 pm 02:35 PM

java

How to determine whether a file is in xml format in java

The method to determine whether a file is in XML format in Java is: first create a parser object through "DocumentBuilderFactory", then use the "parse()" method to parse the file, for example: "parse(file)", and finally make an exception based on the returned information Just judge.

Nov 21, 2019 pm 02:26 PM

java xml judgment document Format

How to delete files in java

In Java, you can use the file.delete(); method to delete files. When the delete() method is called, the file is deleted directly, regardless of whether the file exists, and it is executed immediately once called.

Nov 21, 2019 pm 02:18 PM

java

How to determine whether a string is a url in java

The method to determine whether a string is a URL in Java is: first use the string to set a regular expression, then compile the regular expression and create a matching pattern through the "Pattern.compile" method, and finally use the "matches()" method according to the matching pattern Just match the string.

Nov 21, 2019 pm 02:05 PM

java url judgment character

How to read files in java

Methods for reading files in java: 1. Read by using the [java.io] method, relative to the relative path of the current user directory; 2. Read by using the [java.lang.ClassLoader] method, relative to the classpath The relative path to read.

Nov 21, 2019 pm 01:58 PM

java read file

How to determine whether a number is prime (prime number) in java

The method to determine whether a number is a prime number (prime number) in Java is: first determine whether the number is an even number, if so, return directly, and then start from the next number with a step size of 2 until the arithmetic square root of n. If it cannot be divided, it is a prime number.

Nov 21, 2019 pm 01:42 PM

java judgment prime number prime numbers

How to intercept the first digits of a string in java

In Java, you can use the substring() method to intercept the first few digits of a string. The substring() method returns the substring of the string. Set the starting index to 0 in the substring() method to intercept from the beginning of the string.

Nov 21, 2019 pm 01:38 PM

java

How to determine whether a file is empty in java

The way to determine whether a file is empty in Java is: first, you can create a file object to save the file path, and then use the return value of the "length" method to determine, such as: "file.length". If the file is empty, Then the "length" method will return 0.

Nov 21, 2019 pm 01:28 PM

java Is empty judgment document method

Is the file empty in java?

In Java, you can use the return value of the length() method to determine whether the file is empty. If the file does not exist or the file is empty, the length() method returns 0.

Nov 21, 2019 pm 01:27 PM

java

How to determine whether an array is empty in java

The way to judge whether an array is empty in Java is: if it is a one-dimensional array, it needs to be judged based on the array length, such as "array.length"; if it is a two-dimensional array, it needs to be judged based on the array length of the first row, such as: "array[0" ].length", if the length is 0, the array is empty.

Nov 21, 2019 pm 01:17 PM

java Is empty judgment array method

Java determines whether it is a directory

In Java, you can use the exists() method to determine whether a file or directory exists, and then use the isDirectory() method to check whether the object is a folder. The return value of these two methods is of boolean type, if so, it returns true, otherwise it returns false.

Nov 21, 2019 pm 01:15 PM

java

Java reads txt Chinese garbled characters

Solution to java reading txt Chinese garbled characters: 1. Set the java project and txt file encoding to be unified to utf-8. 2. Use InputStreamReader (new FileInputStream (fileUrl), "utf-8") to set the text to utf-8 encoding.

Nov 21, 2019 pm 12:01 PM

java Garbled characters