Java new file ioexception

Содержание

Class File
Interoperability with java.nio.file package
Java IOException
How IOException Work in Java?
Constructors of IOException in Java
Examples to Implement of Java IOException
Example #1
Example #2
Example #3
Example #4
Conclusion
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Class File

The conversion of a pathname string to or from an abstract pathname is inherently system-dependent. When an abstract pathname is converted into a pathname string, each name is separated from the next by a single copy of the default separator character. The default name-separator character is defined by the system property file.separator , and is made available in the public static fields separator and separatorChar of this class. When a pathname string is converted into an abstract pathname, the names within it may be separated by the default name-separator character or by any other name-separator character that is supported by the underlying system.

A pathname, whether abstract or in string form, may be either absolute or relative. An absolute pathname is complete in that no other information is required in order to locate the file that it denotes. A relative pathname, in contrast, must be interpreted in terms of information taken from some other pathname. By default the classes in the java.io package always resolve relative pathnames against the current user directory. This directory is named by the system property user.dir , and is typically the directory in which the Java virtual machine was invoked.

The parent of an abstract pathname may be obtained by invoking the getParent() method of this class and consists of the pathname’s prefix and each name in the pathname’s name sequence except for the last. Each directory’s absolute pathname is an ancestor of any File object with an absolute abstract pathname which begins with the directory’s absolute pathname. For example, the directory denoted by the abstract pathname «/usr» is an ancestor of the directory denoted by the pathname «/usr/local/bin» .

For UNIX platforms, the prefix of an absolute pathname is always «/» . Relative pathnames have no prefix. The abstract pathname denoting the root directory has the prefix «/» and an empty name sequence.
For Microsoft Windows platforms, the prefix of a pathname that contains a drive specifier consists of the drive letter followed by «:» and possibly followed by «\\» if the pathname is absolute. The prefix of a UNC pathname is «\\\\» ; the hostname and the share name are the first two names in the name sequence. A relative pathname that does not specify a drive has no prefix.

Instances of this class may or may not denote an actual file-system object such as a file or a directory. If it does denote such an object then that object resides in a partition. A partition is an operating system-specific portion of storage for a file system. A single storage device (e.g. a physical disk-drive, flash memory, CD-ROM) may contain multiple partitions. The object, if any, will reside on the partition named by some ancestor of the absolute form of this pathname.

A file system may implement restrictions to certain operations on the actual file-system object, such as reading, writing, and executing. These restrictions are collectively known as access permissions. The file system may have multiple sets of access permissions on a single object. For example, one set may apply to the object’s owner, and another may apply to all other users. The access permissions on an object may cause some methods in this class to fail.

Instances of the File class are immutable; that is, once created, the abstract pathname represented by a File object will never change.

Interoperability with java.nio.file package

The java.nio.file package defines interfaces and classes for the Java virtual machine to access files, file attributes, and file systems. This API may be used to overcome many of the limitations of the java.io.File class. The toPath method may be used to obtain a Path that uses the abstract path represented by a File object to locate a file. The resulting Path may be used with the Files class to provide more efficient and extensive access to additional file operations, file attributes, and I/O exceptions to help diagnose errors when an operation on a file fails.

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Java IOException

Java IOException or IOException usually provides help for some system input and output, which are through the data streams, file system and the serialization etc. This is the method of the java.util.scanner java class which actually returns the IOException, and it is the last one thrown by some Scanner’s underlying Readable. This IOException method will return the NULL value only if no such exception actually exists.

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Public IOException ioException()

A return value of the IOException:

The IOException method/function will return the last exception, which is actually thrown by the scanner’s readable/readables.

How IOException Work in Java?

The IOException of the Java language works by providing some help for some of the inputs and outputs which are available throughout the data streams, serialization and the file system. The IoException() method/functioin works by returning the last thrown Scanner’s underlying readable concept of the IOException. The IOException() method/function will return the NULL value only if no exception is available at all.

How to Avoid IOException?

Using the Try/Catch concept of the Java Programming Language, we can handle the IOException . This is a concept of avoiding the IOException.

Constructors of IOException in Java

Usually, the constructor helps in initializing an object just after the creation of the object creation. It is similar/same syntactically to a specific method/function, but the constructor is having some difference. That is having the same as its class which is having no return type. Actually, there is no need for any constructors invoking explicitly, and these will be invoked automatically at instantiation time.These constructors throw some exceptions.

1. IOException(): This is the normal constructor that constructs one of the new IOException and its stack tracing, which is to be filled in.

2. IOException(Throwable): The Throwable constructor helps in constructing one of the new class instance along with its detailed cause, which is going to filled in. Here “Throwable” parameter is the cause.

3. IOException(String): The String constructor of the IOException() helps construct one of the new IOException along with its stack tracing and with the detailed message: filled.

4. IOException(IntPtr, JniHandleOwnership): This constructor helps in creating the managed representations of some JNI objects, and the runtime calls them. The IntPtr will contain some Java Native Interface (JNI) for the object reference purpose. The JniHandleOwnership parameter indicates handling the javaReference.

5. IOException(String, Throwable): The constructor helps in constructing one of the new class instance along with some detailed message and with cause filling. Here, the String parameter is the message, and the Throwable parameter is the cause.

Examples to Implement of Java IOException

Below are the examples of Java IOException:

Example #1

This is the java program example of implementing the illustration of the ioException() method/function of some Scanner class/classes in the Java Programming Language without using any parameter. Here at first, java util is imported to use all the libraries of the Java Programming Language. Then pavankumarsake1 class is created with the Exception throwing concept. Then s1 string variable is created with the string value. Then scanner1 variable is created with the help of the s1 string variable. Then scanner.nextLine() is created to print the new line, and then scanner.ioException() is used to check whether IO Exception is present or not. Then scanner will be closed using a scanner.close() function.

import java.util.*; public class pavansake1 < public static void main(String[] args) throws Exception < System.out.println(" \n "); String s1 = "Hey! I'am from EDUCBA"; Scanner scanner1 = new Scanner(s1); System.out.println("" + scanner1.nextLine()); System.out.println("" + scanner1.ioException()); scanner1.close(); >>

Example #2

This is the Java example of illustrating the ioException() method along with some of its constructors of the Scanner class in the Java Programming Language without the parameter mentioning. Here at first, java.util.* is imported to import all the functions of the library. Then public class “pavansake1” is created by throwing the exception concept. In the throwing exception, a string s11 is created with some string value. Then a scanner variable is created with the help of the s11 variable to use it as an alternative similar one. Then the ioException() variable is used to show only if there is some IO exception.

import java.util.*; public class pavansake1 < public static void main(String[] argv) throws Exception < System.out.println("\n"); String s11 = "EDUCBA EDUCBA. "; Scanner scanner11 = new Scanner(s11); System.out.println("" + scanner11.nextLine()); System.out.println("" + scanner11.ioException()); scanner11.close(); >>

Example #3

This is the example of implementing the IOException along with the constructor in it, but this example will provide a compilation error due to an issue. Here a class “Employee1” is created whose constructor will throw one of the IOException, and it is instantiating the class which is not handling our exception. So the compilation leads to the compile run time error. Some Java libraries are imported at first, and then private class and public class are created to handle the IOException, but here exception is not handled, so the error occurred.

import java.io.File; import java.io.FileWriter; import java.io.IOException; class Employee1 < private String name1; private int age1; File empFile1; Employee1(String name1, int age1, String empFile1) throws IOException< this.name1 = name1; this.age1 = age1; this.empFile1 = new File(empFile1); new FileWriter(empFile1).write("Employee name is "+name1+"and age is "+age1); >public void display() < System.out.println("Name: "+name1); System.out.println("Age: "+age1); >> public class ConstructorExample1 < public static void main(String args[]) < String filePath1 = "samplefile.txt"; Employee emp1 = new Employee("pksake", 25, filePath); >>

Example #4

This is the example that is very much similar to example 3. To make example 3 to work, we are wrapping the line’s instantiation within the try-catch or the throw exception.

import java.io.File; import java.io.FileWriter; import java.io.IOException; class Employee1 < private String name1; private int age1; File empFile1; Employee1(String name1, int age1, String empFile1) throws IOException< this.name1 = name1; this.age1 = age1; this.empFile1 = new File(empFile1); new FileWriter(empFile1).write("Employee name is "+name1+"and age is "+age1); >public void display() < System.out.println("Name: "+name1); System.out.println("Age: "+age1); >> public class Employee11 < public static void main(String args[]) < String filePath1 = "file1.txt"; Employee1 emp1 = null; try< emp1 = new Employee1("pksake", 26, filePath1); >catch(IOException ex1) < System.out.println("The specific file will not be found"); >emp1.display(); > >

Conclusion

I hope you have learned the definition of Java IOException and its syntax and explanation, How the IOException works in Java Programming Language and its constructors, Java IOException examples, and How to avoid the IOException, etc.