Is there a way to create package-info.java for existing packages in one move in eclipse?

There is no easy way to do this as far as I know, at least "the right way."

What you can do as a shortcut is right-click package-info.java and click "Copy." Then you can use the keyboard shortcut to paste the package-info.java in any package. Eclipse automatically changes the package org.whatever.pkgname; command to match the package you paste the java file into.

It's counter-intuitive, but Eclipse's "New Java Package" dialog with its option to create a package-info.java works for existing packages, too.

Just right-click the existing package, select New > Package, and leave everything except the "Create package-info.java" checkbox unchanged.

This will produce a package-info.java that's pre-populated with the correct package name and an empty javadoc comment block (possibly with @author tags and similar default content depending on your settings). Works even if you don't have an existing file to copy from. Tested with Eclipse Oxygen.

Just copy a package-info.java file (via Ctrl+C and Ctrl+V) from one package to another package. Eclipse automatically corrects the package declaration in the copied package-info.java file.