Trouble with project - new to java

You have a few mistakes (aside from missing curly braces that I added in my edit).

1. sCurrentLine.split("\t") - There are two errors here. The first error is that you need to escape the slash character. Therefore, the correct expression should be "\\t". However, your file might not be tabbed delimited. Therefore, for space-delimited text, you should use "\\s", " ", or "\\s+". If you are not sure how many spaces, the last expression is the best because it will work with one-or-more spaces.

2. Integer.parseInt(...) - This needs to be Double.parseDouble() because the values in the file are floating-point numbers, not integers.

3. System.out.println(balance) inside viewWallet() is incorrect - That line displays the object, not the contents because arrays do not have a way to override toString(). So, you have to iterate through the balance array and display it contents. The simplest way is like this:

for(double value : balance) {
    System.out.println(value);
}

This will display all the values in the array in separate lines. If the array is empty, it will skip altogether.

Corrected code

import java.io.*;
import java.util.*;

public class Main {
    static Scanner userInputInt = new Scanner(System.in);
    static Scanner userInputString = new Scanner(System.in);
    static Scanner userInputDouble = new Scanner(System.in);

    public static void main(String[] args) { // throws Exception
        int userChoice = getUserChoice();
        switch (userChoice) {
        case 1:
            viewWallet();
            break;
        }
    }

    // This method asks and returns what the user wants to do
    public static int getUserChoice() {
        System.out.println("****************************************************************");
        System.out.println("****************************************************************");
        System.out.println("************ Crypto Wallet **********");
        System.out.println("****************************************************************");
        System.out.println("****************************************************************");
        System.out.println("");
        System.out.println("What do you want to do?");
        System.out.println("(1) View wallet");
        System.out.println("(2) Look up the balance of a given crypto");
        System.out.println("(3) Add new cryptos");
        System.out.println("(4) Remove an existing crypto");
        System.out.println("(5) Update wallet");
        System.out.println("****************************************************************");
        System.out.print("Please enter your choice (1, 2, 3, 4, or 5): ");
        return userInputInt.nextInt();
    }

    // This method is called for user choice 1
    public static void viewWallet() {
        double[] balance = readCryptoBalance();
        for(double value : balance) {
            System.out.println(value);
        }
    }

    // This method reads and returns the crypto balances from the file
    public static double[] readCryptoBalance() {
        double[] temp = new double[100];
        int lineNumber = 0;
        try {

            BufferedReader myFile = new BufferedReader(new FileReader("wallet.txt"));
            String sCurrentLine;
            while ((sCurrentLine = myFile.readLine()) != null) {
                String[] tokens = sCurrentLine.split("\\s+");
                temp[lineNumber] = Double.parseDouble(tokens[1]);
                lineNumber++;
            }
            myFile.close();
        } catch (IOException e) {
            System.out.println("Error reading crypto balance: " + e.getMessage());
        }
        double[] balance = new double[lineNumber];
        System.arraycopy(temp, 0, balance, 0, lineNumber);
        return balance;
    }
}

Disclaimer: the contents of the file I created to test was exactly as the string provided by the OP (minus the double quotes) BTC 1.3426 ETH 5.2519 XRP 158.5000. Therefore, my solution assumed space-delimited string in a single line. Add a carriage return/line feed after each number to have distinct lines for the different crypto currency values.