Android class where i was wrong

Question

public class temp 
{
 public int data0;//整数
 public int data1;//小数
 public int data2;
 public int data3;
 public long firsttime;
 public temp(int type,int data0, int data1, int data2, int data3,
 long firsttime) {
 super();
 this.data0 = data0;
 this.data1 = data1;
 this.data2 = data2;
 this.data3 = data3;
 this.firsttime = firsttime;
 }
}
public class ShareDate {
 public static temp mtemp=null;
 public static date mdate=null;
}

the problem is in MainActivity I did like this

ShareDate.mtemp.date0=20; 

then the program was stopped unexpected. I don't know where it's wrong?

• Lucifer: take a breath while editing @Krishnabhadra
• nhahtdh: Do you even create an instance of temp class?
• Lucifer: @Krishnabhadra, i am just saying you to do meaningful edit :)
• ninjiaquan: what is mean ? i was use class ShareDate it in MainActivity ShareDate class include static temp mtemp. i mean why i can't evaluation for mtemp.date0 ?

Answer 1

where is your initialization code?

mtemp=new temp();

A class's object must be initialized to use its data member/Methods.

• ninjiaquan: but mtemp is static why it need initiaiztion?
• ninjiaquan: you mean in class ShareDate? i was initialized as null ,then in MainActivity i still cannot evaluation; like this ShareDate.mtemp.date0=20
• ninjiaquan: oh thanks your answer helped me ,now it's ok .it's must that initialize first.

Answer 2

You need to initialize before object use.. There is no initialization code..

mtemp=new temp();

And why u use constructor?

If you use ,

ShareDate.mtemp.date0=20; like this ,,

no need a constructor.