Lesson 21- Class Wrappers + Variable conversion

Topics Discussed: Class Wrappers and changing types using toString / parseint / parseDouble

Source code for Lesson 21:

class testing{
	public static void main(String[] args){
	    //double d = null; //Can't do this, double is a primative type
		Double d = null;
		int k=5;
 
		if(k < 5 ) {
			d+=10;
		}
		else{
			k+=10;
		}
 
		if(d==null){
			//do Something
		}
 
		System.out.println(d+" - " + k);
 
 
		//double d=4.0
		//String str = "" ; 
 
		//str = appendOhai(Double.toString(d));
	}
	public static String appendOhai(String str){
		str +="Ohai";
		return str;
	}
}

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Class wrappers:

Class wrappers exist to help us manipulate primitives of similar type. Some code that you’ll want to be aware of is

Double d = null; // Class wrappers can accept null values
Double.parseInt(d); //Class wrappers can be used to change the variable type as long as the data is the same
**NOTE** When changing variable type, there can be a loss of precision.   Example
double d= 4.779;
int i = Double.parseInt(d); // I would now be equal to 4.   Everything after the decimal would be dropped.