How to compare a parameter with an object in Java?

Question

Would anyone know how to compare an parameter with an object? I've been trying to do it following the instructions given in the last question here: http://prntscr.com/1zaq0y But, doesn't seem to wrork.

public class Classification
    {
        String changes;
        String rating;
        String description;

    Classification()
    {
        rating = "G";
        description = "Suitable for general audiences";
    }

    Classification(String must)
    {
        if(must != "G" || must!= "PG" || must!="M")
        {
            throw new NullPointerException ("Not equal");
        }
        rating = must;
        if(rating == "G")
        {
            description = "Suitable for general audiences";
        }
        if(rating == "PG")
        {
            description = "Parental guidance recommended"; 
        }
        if(rating == "M")
        {
            description = "Suitable for mature audiences";
        }
    }

    Classification (int num, String para)
    {
        if(num!= 13 || num!= 15 || num!=16 || num!=18)
        {
            throw new IllegalArgumentException("Not equal");
        }
        if(para==null)
        {
            throw new NullPointerException("String is null");
        }
        if(num == 16)
        {
            rating = "R";
            description = para;
        }
        changes = rating + num;
    }

    void printClassification()
    {
        print("Rated " + rating + ": " + description);
    }

    void derestrict()
    {
        if(rating == "M")
        {
            rating = "PG";    
        }
        if(rating == "PG")
        {
            rating = "G";
        }
        if(rating == "G")
        {
            throw new IllegalArgumentException("G is least restrictive");
        }
        if(changes == "R18")
        {
            changes = "R16";
        }
        if(changes == "R15")
        {
            changes = "R13";
        }
    }

    Classification isLessRestrictive(Classification compare)
    {
        if(compare==null)
        {
            throw new NullPointerException ("Classification para is null");
        }
        if(changes<compare)
        {
            return true;
        }
        return false;
    }
}

What is the difference between a "parameter" and an "object"??? — Hot Licks, Oct 23 '13 at 23:42

nhgrif · Answer 1 · 2013-10-23T23:55:16.107

1

When comparing Strings in Java, you need to use equals().

For example,

if(must != "G" || must!= "PG" || must!="M")

Should instead be

if(!"G".equals(must) || !"PG".equals(must) || !"M".equals(must))

And

if(rating == "G")

Would look like this:

if("G".equals(rating))

edited Oct 23 '13 at 23:55

answered Oct 23 '13 at 23:43

nhgrif

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1

Not to nitpick since it doesn't affect the answer but `if ("G".equals(rating))` is safer because rating can be null. – Radiodef Oct 23 '13 at 23:53
@Radiodef Mmm, good point. I'll change the answer. – nhgrif Oct 23 '13 at 23:54

How to compare a parameter with an object in Java?

1 Answers1