To delete a file in Java, use the delete() method:
import java.io.File; // Import the File class
public class DeleteFile {
public static void main(String[] args) {
File myObj = new File("filename.txt");
if (myObj.delete()) {
System.out.println("Deleted the file: " + myObj.getName());
} else {
System.out.println("Failed to delete the file.");
}
}
}The output will be:
Deleted the file: filename.txt
In the previous chapter, you learned how to create and write to a file.
In the following example, we use the Scanner class to read the contents of the text file we created in the previous chapter: Continue reading Java Read Files
To create a file in Java, you can use the createNewFile() method. This method returns a boolean value: true if the file was successfully created, and false if the file already exists. Note that the method is enclosed in a try...catch block. This is necessary because it throws an IOException if an error occurs (if the file cannot be created for some reason): Continue reading Java Create and Write To Files
File handling is an important part of any application.
Java has several methods for creating, reading, updating, and deleting files.
The File class from the java.io package, allows us to work with files.
To use the File class, create an object of the class, and specify the filename or directory name: Continue reading Java Files
In the List Sorting Article, you learned how to sort lists alphabetically and numerically, but what if the list has objects in it?
To sort objects you need to specify a rule that decides how objects should be sorted. For example, if you have a list of cars you might want to sort them by year, the rule could be that cars with an earlier year go first.
The Comparator and Comparable interfaces allow you to specify what rule is used to sort objects.
Being able to specify a sorting rule also allows you to change how strings and numbers are sorted.
Lambda Expressions were added in Java 8.
A lambda expression is a short block of code which takes in parameters and returns a value. Lambda expressions are similar to methods, but they do not need a name and they can be implemented right in the body of a method.
Threads allows a program to operate more efficiently by doing multiple things at the same time.
Threads can be used to perform complicated tasks in the background without interrupting the main program.
A regular expression is a sequence of characters that forms a search pattern. When you search for data in a text, you can use this search pattern to describe what you are searching for.
A regular expression can be a single character, or a more complicated pattern.
Regular expressions can be used to perform all types of text search and text replace operations.
Java does not have a built-in Regular Expression class, but we can import the java.util.regex package to work with regular expressions. The package includes the following classes:
Pattern Class – Defines a pattern (to be used in a search)Matcher Class – Used to search for the patternPatternSyntaxException Class – Indicates syntax error in a regular expression patternWhen executing Java code, different errors can occur: coding errors made by the programmer, errors due to wrong input, or other unforeseeable things.
When an error occurs, Java will normally stop and generate an error message. The technical term for this is: Java will throw an exception (throw an error).
Wrapper classes provide a way to use primitive data types (int, boolean, etc..) as objects.
The table below shows the primitive type and the equivalent wrapper class:
| Primitive Data Type | Wrapper Class |
|---|---|
| byte | Byte |
| short | Short |
| int | Integer |
| long | Long |
| float | Float |
| double | Double |
| boolean | Boolean |
| char | Character |
Sometimes you must use wrapper classes, for example when working with Collection objects, such as ArrayList, where primitive types cannot be used (the list can only store objects): Continue reading Java Wrapper Classes