Java variable assignment

Question

My code prints 0 instead of size and year. What am I doing wrong? Basically I want it to return those but I'm not sure what I'm doing.

public class House {
private int year;
private int size;
private static int nbrOfHouses; 
public static final int MIN_SIZE =10; 

public House(int _year,int _size){
    _year = year;
    _size = size;
}
public static int getNbrHouses(){ 
    return nbrOfHouses;
}
public int getYear(){
    return year;
    }
public int getSize(){
    return size;
}
}


House[] myHouse = new House[10];{
  myHouse[0] = new House(1902, 120);
  myHouse[1] = new House(1954, 180);
  myHouse[2] = new House(1995,90);

  for(int i=0; i< myHouse.length; i++){
        if(myHouse[i]!=null){
          System.out.println(myHouse[i].getYear());

you may also use advance for loop for(House house: myHouse){ System.out.println(house.getYear()); } — Nilanchala
– Nilanchala, Commented Sep 2, 2013 at 4:54

pfrank · Accepted Answer · 2013-09-02 04:55:03Z

5

This is backwards:

public House(int _year,int _size){
    _year = year;
    _size = size;
}

Should be:

public House(int _year,int _size){
    year = _year;
    size = _size;
}

or better yet:

public House(int year,int size){
    this.year = year;
    this.size = size;
}

answered Sep 2, 2013 at 4:55

pfrank

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Comments

hotforfeature · Accepted Answer · 2013-09-02 04:53:06Z

4

In your constructor, you are not assigned the class variables correctly. Do this:

public House(int _year,int _size){
    year = _year;
    size = _size;
}

You're assigned the arguments to the class variables (which are initialized to 0). Since the class variables are initialized at 0 and are not modified, that's why it prints 0.

As mentioned by @pfrank, Java naming conventions don't usually have the underscore. A more conventional way to code it is with the this keyword.

public House(int year,int size){
    this.year = year;
    this.size = size;
}

answered Sep 2, 2013 at 4:53

hotforfeature

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Comments

Rohit · Accepted Answer · 2013-09-02 04:54:10Z

2

use

public House(int _year,int _size){

this.year = _year;
this.size = _size;
}

answered Sep 2, 2013 at 4:54

Rohit

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1 Comment

DanielX2010 Over a year ago

that wont work, since the arguments of the constructor are _year and _size

Subhrajyoti Majumder · Accepted Answer · 2013-09-02 04:53:33Z

1

Fields are not initialized properly.

public House(int _year,int _size){
    this.year = _year;
    this.size = _size;
}

answered Sep 2, 2013 at 4:53

Subhrajyoti Majumder

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1 Comment

hotforfeature Over a year ago

this.year = _year Careful of the argument name

Sotirios Delimanolis · Accepted Answer · 2013-09-02 05:00:31Z

1

The Java Language Specification section 15.26 states

AssignmentExpression:
    ConditionalExpression
    Assignment

Assignment:
    LeftHandSide AssignmentOperator AssignmentExpression

LeftHandSide:
    ExpressionName
    FieldAccess
    ArrayAccess

AssignmentOperator: one of
    = *= /= %= += -= <<= >>= >>>= &= ^= |=

You always assign from the right hand side to the left hand side. This

public House(int _year,int _size){
    _year = year;
    _size = size;
}

is therefore reversed and should be

year = _year;
size = _size;

Also, because instance fields are by default initialized to 0 for primitive types, all your int fields have a value of 0.

edited Sep 2, 2013 at 5:00

answered Sep 2, 2013 at 4:53

Sotirios Delimanolis

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