Do not quite understand the value of student property age is when given ah ?

a, b is not initialized, not allocated memory space, the error can be understood .
name and age are not in the new student when he allocated memory space? int default 0, string default null
But if I want in the database ( the database is to allow the float is null ) then save the salaries salary ,
0.0 represents wages made ​​it to 0,
null said wages did not send ,
how this achieved?

  public class test {
  
  	/**
  	 * @param args
  	 */
  	public static void main(String[] args) {
  		// TODO Auto-generated method stub
  		Person person=new Person();
  		System.out.println(person.age);
  		System.out.println(person.name);
  		System.out.println(person.salary);
  		
  		int a;
  		System.out.println(a);
  		String b;
  		System.out.println(b);
  	
  	}
  
  }
  
  class Person {
  	public String name;
  	public int age;
  	public float salary;
  
  	
  }
  
  

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their landlord to solve the problem
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float as the value of null, Float is not , is the basic data types and encapsulation java type is not the same, the specific differences between a lot of investigation Kazakhstan
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and then study it before posting . .
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can take points yet
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is not my salary would not with a float type , only to turn up with string ?
However, the design of this level in terms of float data type to represent a reasonable wage should be better than string type fishes
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tried it, feel with Float instead of float can be solved . . .