9 replies to this topic

[arunjib]

I atrying to run the following program. I can write a program to validate time with the help of this program. but this program is showing a error message. Please tell me the reason
operator || cannot be applied to boolean,int

class Dates

{

    int dd, mm, yy;

    public Dates()

    {

        dd=0;

        mm=0;

        yy = 0;

    }

    public Dates(int d, int m, int y)

    {

        dd=d;

        mm=m;

        yy=y;

    }

    public boolean validate()

    {

        boolean valid=false;

        if((mm==1||mm==3||mm=5||mm==7||mm==8||mm==10||mm==12) && (dd>=1 && dd<=31))

        valid=true;

        else if ((mm==4||mm==6||mm==9||mm==11)&&(dd>-1&&dd<=30))

        valid=true;

        else if(mm==2&&(yy%4!=0)&&(dd>=1&&dd<=28))

        valid=true;

        else if(m==2 &&(yy%4==0)&&(dd>=1&&dd<=29))

        valid=true;

        return valid;

    }

    public void print()

    {

        System.out.println(dd+"/"+mm+"/"+yy);

    }

}

[wim DC]

You're missing an equal sign (=) at 'mm=5'
You also did dd>-1 instead of dd>=1 at the 2nd if-statement.
Also missing an 'm' at 'm==2' @4th if-statement.

[gregwarner]

In Java, data types are treated more strictly than in C/C++. Int's are not necessarily compatible with booleans.

Here's the offending line:

if((mm==1||mm==3||mm=5||mm==7||mm==8||mm==10||mm==12) && (dd>=1 && dd<=31))

You used the assignment operator with # 5. Needs a double equals sign instead.

[gregwarner]

wimDC beat me to the punch.
*bows to faster keyboard skills*

[fayyazlodhi]

gregwarner said:

In Java, data types are treated more strictly than in C/C++. Int's are not necessarily compatible with booleans.

Here's the offending line:

if((mm==1||mm==3||mm=5||mm==7||mm==8||mm==10||mm==12) && (dd>=1 && dd<=31))

You used the assignment operator with # 5. Needs a double equals sign instead.

The = mistakenly placed instead of == is such a frequent mistake in c, java and quite a few other languages, that a coding convention / practice was developed by linux kernel (i think) and was widely adopted.

ALWAYS put the CONSTANT in a comparison on LEFT side.

if (x ==4 ) // instead of this


if (4==x) // use this

You will always get a compile time error if you mistakenly type a single =

[arunjib]

Thank you for finding out my error. I have corrected the mistake. Now my class is compiles successfully.

wim DC said:

You're missing an equal sign (=) at 'mm=5'
You also did dd>-1 instead of dd>=1 at the 2nd if-statement.
Also missing an 'm' at 'm==2' @4th if-statement.

[arunjib]

Thank you for finding out my error. I have corrected the mistake. Now my class is compiles successfully.

gregwarner said:

In Java, data types are treated more strictly than in C/C++. Int's are not necessarily compatible with booleans.

Here's the offending line:

if((mm==1||mm==3||mm=5||mm==7||mm==8||mm==10||mm==12) && (dd>=1 && dd<=31))

You used the assignment operator with # 5. Needs a double equals sign instead.

[arunjib]

Thank you for finding out my error. I have corrected the mistake. Now my class is compiles successfully.

fayyazlodhi said:

The = mistakenly placed instead of == is such a frequent mistake in c, java and quite a few other languages, that a coding convention / practice was developed by linux kernel (i think) and was widely adopted.

ALWAYS put the CONSTANT in a comparison on LEFT side.

if (x ==4 ) // instead of this


if (4==x) // use this

You will always get a compile time error if you mistakenly type a single =

[arunjib]

Here is my corrected code.

Now the question is, how can I get output if the date entered false.

If i enter a invalid date, I want to get a message "You have entered invalid date" instead of the date i have entered.
Suppose i have input date as 32/14/2001 i am getting the output as 32/14/2001. But i want to get output as "You have entered invalid date"

class Dates

{

    int dd, mm, yy;

    public Dates()

    {

        dd=0;

        mm=0;

        yy = 0;

    }

    public Dates(int d, int m, int y)

    {

        dd=d;

        mm=m;

        yy=y;

    }

    public boolean validate()

    {

        boolean valid=false;

        if((mm==1||mm==3||mm==5||mm==7||mm==8||mm==10||mm==12) && (dd>=1 && dd<=31))

        valid=true;

        else if ((mm==4||mm==6||mm==9||mm==11)&&(dd>-1&&dd<=30))

        valid=true;

        else if(mm==2&&(yy%4!=0)&&(dd>=1&&dd<=28))

        valid=true;

        else if(mm==2 &&(yy%4==0)&&(dd>=1&&dd<=29))

        valid=true;

        return valid;

    }

    public void print()

    {

        System.out.println(dd+"/"+mm+"/"+yy);

    }

}

[gregwarner]

fayyazlodhi said:

ALWAYS put the CONSTANT in a comparison on LEFT side.
You will always get a compile time error if you mistakenly type a single =

I like this thought.