File File(File, String) in Java

File(File, String): This method is available in the java.io.File class of Java.

Syntax:

java.io.File.File(File parent, String child)

This method takes two arguments. This method creates a new File instance from a parent abstract pathname and a child pathname string.

Note: If a parent is null then the new File instance is created as if by invoking the single-argument File constructor on the given child pathname string.

Otherwise the parent abstract pathname is taken to denote a directory, and the child pathname string is taken to denote either a directory or a file.

Parameters: Two parameters are required for this method.

parent: The parent abstract pathname.

child: The child pathname string.

Throws:

NullPointerException - If the child is null

Approach 1: When no exception

Java

import java.io.File;
import java.net.URI;
import java.net.URISyntaxException;

public class FileParent {
    public static void main(String[] args) 
                 throws URISyntaxException {

        URI uri = new URI("file:/D/hello");
        File parent = new File(uri);
        String child = "java";
        File file = new File(parent, child);

        System.out.println(file);
    }
}

Output:

\D\hello\java

Approach 2: NullPointerException

Java

import java.io.File;
import java.net.URI;
import java.net.URISyntaxException;

public class FileParent {
    public static void main(String[] args) 
              throws URISyntaxException {

        URI uri = new URI("file:/D/hello");
        File parent = new File(uri);
        String child = null;
        File file = new File(parent, child);

        System.out.println(file);
    }
}

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.base/java.io.File.<init>(File.java:362)