Exception Error need help fixing

[skinnybones]

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[hardwired]

I put both classes in the same file, changed their names, compiled, ran and got this in the console:

Code:

C:\jexp>javac playrx.java

C:\jexp>java PlayRx
Exception in thread "main" java.lang.NullPointerException
        at ShowRx.guess(playrx.java:69)
        at PlayRx.main(playrx.java:20)

Count down to line 69 to find

Code:

        if ( !guess.equals(strings[currentString]) &&
                           strings[currentString].contains(guess) )

Something in this line was null. It is a member variable which was hidden/shadowed by a local variable.

Code:

class ShowRx
{
    // Member variable declaration.
    // Member variables have class scope.
    private String[] strings;
    ...
    public ShowRx()
    {
        // Local variable of same name is declared and instantiated.
        // This hides/shadows the member variable with same name and
        // its (the member variable) value remains null. The scope of
        // this local variable is within the curley braces of this
        // constructor, ie, no one outside the constructor can see
        // this local variable.
        String[] strings = {
            "cat", "dog", "mouse", "bear", "moose", "bird",
            "frog", "fish", "slug", "emu"
        };

How to fix this?

Code:

    private String[] strings;
    ...
    public ShowRx()
    {
        // Instantiate the member variable.
        strings = new String[] {
            "cat", "dog", "mouse", "bear", "moose", "bird",
            "frog", "fish", "slug", "emu"
        };

Now everyone in ShowRx can see "strings" and it has been instantiated and its value is therefore non–null.

[skinnybones]

Thanks for the help