Copy files containing one of the word from list

I have large code base in front of me. In this I want to find the files(path) that contain the class definition and copy the file to a folder. I have a list of class names(about 50) to look for.

I've tried using grep like

cp $(grep --include=\*.java -rl . -e "class SplashScreen" *) --parents -t ./dest-folder

It works, but it takes a lot of time to find even one class through code.
I could write a script looping though every class name will take a long time and i don't want to do it manually for every class.

Is there a better way to do this?

Assuming that you have a list of class names in a file list.txt (one class name per line):

MyClass1
MyClass2
MyInterface1

it is possible to process this file to build up a regexp to select the class names and store it into a variable:

$ class_names="$(cat list.txt|tr '\n' '#'|sed 's/#/\\|/g')"

Then you can run your script using grep or you could use find.

$ cp $(find ./src -type f -name "*.java" -exec grep -l "\(class\|interface\) \($class_names\)" {} +) --parents -t ./mydest-dir

Or, without the temporary variable the final command may look like this:

$ cp $(find ./src -type f -name "*.java" -exec grep -l "\(class\|interface\) \($(cat list.txt|tr '\n' '#'|sed 's/#/\\|/g')\)" {} +) --parents -t ./mydest-dir

To make sure the required files are copied successfully, use the same find:

$ find ./mydest-dir -type f -name "*.java"

Use -f to define a file of patterns to apply. You can include regex metacharacters in the patterns.
You can use shopt -s globstar to access filenames at indeterminate depth.

If pats is the name of your pattern file,

shopt -s globstar
cp --parents -t ./dest-folder $( grep -l -f pats **/*.java )