How to define file path in global.properties file?

I have a global.properties file and have to define the file path inside this properties file.

SheetPath=C:\\Users\\test\\Automation-Scripts\\DataTable.xlsx

This is an absolute path but require a way to define a relative path that can be consumed while calling.

Properties file:

testPath=API_Files/duplicateToken.json

Load the properties file:

public static Properties readProperties = new Properties();
public static void loadPropertiesFile() {
    File propertiesFile = new File(location of properties file);
    try {
        FileInputStream fileInput = new FileInputStream(propertiesFile);
        readProperties.load(fileInput);
    } catch (Exception e) {
        Logger.LogError("Error in loading the Properties file" + e.getMessage());
    }
}

Read the properties file and get absolute path:

 String testPath = readProperties.getProperty("testPath").trim();
 File absolutePath =  new File(System.getProperty("user.dir") + testPath);
 System.out.println(absolutePath);

Sample output:

C:\Users\test\Automation-Scripts\duplicateToken.json