how to deal with long ,float , double

/* This  Program is a simple java Application which
shows how to java performs arithmetic operations on double,float
(we can assign a long value to float,double but not 
possible to float value assign to long,double directly)*/
package datatypes;

public class DoubleLong {

   
    public static void main(String[] args) {
//        float i=22.0,j=33.0; //is this okay ?
        float i=22.0F,j=33.0F;
        long l1=20L,l2=30L;
        double b1=90.9,b2=100.9;
        i=l1;
        i= i + j ; // This executes without any problem.
     //     l1 = i + j;  //does this converts i + j to long ? why ?
        l1 =(long)( i + j); //explicit cast needed
    //    l1 = i + l2; //what happens here ?
    //    l1 = (long) (i +l2);//l2 will be conveterted to float
        i = l1 + l2; // what happens ? why ?
        i =(int) l1 + l2; //what happens ? why ?
        i =(float) (b1 + b2);
        i = l1 + l2;// here l1 +l2 will be converted to float
        l1 = (long)(b1 + b2); // b1 + b2 has to be casted to long
        b1 = l1 + l2; //no cast is needed here
        b1 =(double) l1 + (double)l2;

    }

}