complicatedCode.java

public List<String> onTabComplete(CommandSender sender, Command command, String label, String[] args) {
    
    // args = ["tp", "colonies", "ci"]; length: 3
    
    List<String> returnArgs = new ArrayList<String>();
    List<String> allOptions = somehowGetPossibleArguments(); 
    
    String[] protectionNameStrings = new String[args.length - 1]{};
    
    // args, 1 = point in args array to start at, copying to protectionNameStrings, point in protectionNameStrings array to copy to, array length - 1
    System.arraycopy(args, 1, protectionNameStrings, 0, args.length - 1);
    
    // protectionNameStrings = ["colonies", "ci"]; length: 2 (ideally, i havent acrtually tested this code)
    
    // Join all protectionNameStrings to one string
    StringBuilder protectionName = new StringBuilder();
    for (String s : protectionNameStrings){
        protectionName.append(s);
    }

    for (String option : allOptions) { 
        // Check if option starts with protectionName.toString()
        // "colonies city" starts with "colonies ci"
        if (option.toLowerCase().startsWith(protectionName.toString())) { 
            // This gets complicated. Need to return argument FROM the current unfinished argument's position.
            // So if the command is "/bp tp protection with long na...", we'd need to only finish the "name" argument, or if it is "/bp tp protection with lo...", we'd need to finish "long name"
            
            // option = "colonies city"
            
            List<String> allPieces = Arrays.asList(option.toLowerCase().split(" "));
            // allPieces = ["colonies", "city"]; length: 2
            List<String> validPieces = new ArrayList<String>();
            
            // System.arraycopy(["colonies", "city"], 1, [], 0, 1 /* 2 - (2 - 1) */); 
            // System.arraycopy(["colonies", "city", "resort"], 1, [], 0, 2 /* 3 - (2 - 1)*/); 
            
            // How many user provided: protectionNameStrings.size() - 1
            // How many the command requires: allPieces.size()
            // How many we provide back: allPieces.size() - (protectionNameStrings.size() - 1)
            System.arraycopy(allPieces, protectionNameStrings.size() - 1, validPieces, 0, allPieces.size() - (protectionNameStrings.size() - 1)); 
            
            // Join all valid pieces to one string
            StringBuilder validPiecesString = new StringBuilder();
            for (String s : validPieces){
                validPiecesString.append(s);
            }
            
            returnArgs.add(validPiecesString); 
        } 
    } 
    
    return returnArgs; 
}