I don’t know which way is preferable:

1. using a private method that uses a return statement which is used inside another method of the same class:

private int calculate(int x)
{
    // random calculation
    return x * x;
}

public void print()
{
    System.out.println(calculate(3));
}

2. changing the value of a private attribute which is used inside another method of the same class:

private int result;
    
private void calculate(int x)
{
    // random calculation
    result = x * x;
}
    
public void print()
{
    System.out.println(result);
}