CODEWITHSUNDEEP
java
user1896464
user1896464

Reputation: 345

Java Interface implementation

This is my first time working with the java interface and im very confused. after reading tutorial online this is what i came up with how to define the interface and implement it but there is red underline on the hours,minutes and seconds. and i cant figure out why its so. 

interface myClock {

    int hours;
    int minutes;
    int seconds;

    public void clock();
    public void clock(int x, int y, int z);
    public void setTime(int x, int y, int z);
    public void incTimeBySec();
    public void incTimeByMins(int x);
    public void display12hr();
    public void  display24hr();
}

class time implements myClock {

    public void clock() {
        hours   = 0;
        minutes = 0;
        seconds = 0;
    }

    public void clock(int x, int y, int z) {
        hours   = x;
        minutes = y;
        seconds = z;
    }

    public void setTime(int x, int y, int z) {
        hours = x;
        minutes = y;
        seconds = z;
    }

    public void incTimeBySec() {    
        if(seconds+1>60) {
            seconds = (seconds+1)-60;
            minutes++;
            hours++;
        } else {
            seconds+=1;
        }
    }
}

Upvotes: 1

Views: 3400

Answers (8)

duffymo
duffymo

Reputation: 308763

Interfaces only define methods. There are no data members, except for statics.

I'd recommend that you learn the Java coding standards. You aren't following them (e.g. class and interface names should be capitalized.)

public interface MyClock {
    void setTime(int x, int y, int z);
    void incTimeBySec();
    void incTimeByMins(int x);
    void display12hr();
    void  display24hr();
}

I would not recommend that you do this, unless you just want to learn about interfaces. The Java Date class implements all these methods better than you ever will. Use what's available to you.

Update: Since JDK 8 interfaces can have default implementations.

Upvotes: 7

ggmax
ggmax

Reputation: 125

you do not initialization you'r variables , you can't do something like second++ when you declare second whit no initial value.

Upvotes: 0

LynAs
LynAs

Reputation: 6537

Error : The blank final field hours may not have been initialized Solution dont put variable in interface. only methods

public interface MyClock {
    void setTime(int x, int y, int z);
    void incTimeBySec();
    void incTimeByMins(int x);
    void display12hr();
    void  display24hr();
}

Upvotes: 0

Joni
Joni

Reputation: 111259

Instance variables, like hours, minutes and seconds here, are part of implementation details. An interface only specifies what methods the implementing classes should have, not how they should implement them. Therefore you cannot declare variables in interfaces. Constants declared using static final are allowed though.

Upvotes: 2

Martin Wilson
Martin Wilson

Reputation: 3386

You can't declare instance variables in an interface. Move them into your implementation instead.

Upvotes: 1

upog
upog

Reputation: 5531

All the variables defined in interface should be public static final

public static final int hours = 0;
public static final  int minutes = 0;
public static final  int seconds  =0;

Ideally you can declare only constants

Upvotes: 1

sanbhat
sanbhat

Reputation: 17622

All the fields defined in interface are by default public static final.

You are getting compile-time error because your you have not given values to the final fields of the interface while declaring them

Upvotes: 1

Lorenzo Baracchi
Lorenzo Baracchi

Reputation: 1978

interfaces cannot have a state!

Upvotes: 5

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