This script finds all the files in which specific fields are used.

MainClass.java

package com.RollUpSummaryFieldFinder;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class MainClass {
	
	static Map<String, Set<String>> matchingFileSet = new HashMap<>();
	static List<String> fieldNames = new ArrayList<String>();
	static Set<String> excludeFolderNamesSet = new HashSet<String>();
	
	public static void main(String[] args){
		File folder = new File("/home/ram/JohnDoe/DEV_SANDBOX/src");
		
		fieldNames.add("Field_One__c");
		fieldNames.add("Field_Two__c");
		
		excludeFolderNamesSet.add("profiles");
		excludeFolderNamesSet.add("permissionsets");
		excludeFolderNamesSet.add("layouts");
		excludeFolderNamesSet.add("objecttranslations");
		excludeFolderNamesSet.add("letterhead");
		excludeFolderNamesSet.add("staticresources");
		excludeFolderNamesSet.add("wave");
		
		try{code
			searchFiles(folder);
		}catch(Exception e){
			System.out.println(e.getMessage());
		}
		
		for(String fileName: matchingFileSet.keySet()){
			System.out.println(fileName +  " uses the below fields: ");
			
			for(String fieldName: matchingFileSet.get(fileName)){
				System.out.println("    " + fieldName);
			}
		}
	}
	
	public static void searchFiles(File folderName) throws FileNotFoundException,IOException{
		boolean printedCurrentFolder = false;
		
		
		for (File fileEntry : folderName.listFiles()) {
			
			if(!printedCurrentFolder){
				System.out.println("Searching files in folder "+ folderName.getName());
				printedCurrentFolder = true;
			}
			
			boolean invalidFile = fileEntry.getName().endsWith("-meta.xml");
			invalidFile = invalidFile || fileEntry.getName().endsWith(".profile");
			invalidFile = invalidFile || fileEntry.getName().endsWith(".png");
			invalidFile = invalidFile || fileEntry.getName().endsWith(".quickAction");
			invalidFile = invalidFile || fileEntry.getName().endsWith(".queue");
			
			if(!invalidFile && fileEntry.isFile()){
				
				System.out.println("Searching file "+ fileEntry.getName());
				
				FileReader fileReader = new FileReader(fileEntry);
				BufferedReader bufferedReader = new BufferedReader(fileReader);
				String line;
				
				while ((line = bufferedReader.readLine()) != null) {
					for(String fieldName : fieldNames){
						if(line.contains(fieldName)){
							if(matchingFileSet.containsKey(fileEntry.getName())){
								matchingFileSet.get(fileEntry.getName()).add(fieldName);
							}else{
								matchingFileSet.put(fileEntry.getName(),new HashSet<String>());
								matchingFileSet.get(fileEntry.getName()).add(fieldName);
							}
						}
					}
				}
				fileReader.close();
			}
	    }
		
		File[] childFolders = getChildDirectories(folderName);
		for (int i = 0; i < childFolders.length; i++) {
			
			if(!excludeFolderNamesSet.contains(childFolders[i].getName().toLowerCase())){
				searchFiles(childFolders[i]);
			}
		}
		
	}
	
	public static File[] getChildDirectories(File folderName){
		List<File> subFolders = new ArrayList<File>();
		String[] names = folderName.list();
		
		for(String name : names){
			
		    if (new File(folderName.getAbsolutePath() + "/" + name).isDirectory()){
		        subFolders.add(new File(folderName.getAbsolutePath() + "/" + name));
		    }
		}
		
		return subFolders.toArray(new File[subFolders.size()]);
	}
}