Can enyone tell me a book to read thats eazy and for 4th grade hurry and help me PLEASE

Acommon algorithm for converting a decimal number to binary is to repeatedly divide the decimal number by 2 and save the remainder. this division is continued until the result is zero. then, each of the remainders that have been saved are used to construct the binary number. write a recursive java method that implements this algorithm. it will accept a value of int and return a string with the appropriate binary character representation of the decimal number. my code: public class lab16{public string converttobinary(int input){int a; if(input > 0){a = input % 2; return (converttobinary(input / 2) + "" +a); } return ""; } }