How to convert String Number Input into Real Number Output

[Hitesh Patel Patel]

import java.util.*;

class MathDemo1 {
	
	public MathDemo1(){}
	
	public static void main(String[] args){		
		String str = null;
		
		if(args != null && args.length > 0){
			str = args[0];
		} else {
		   str = "123";
		}
		
		int result = MathDemo1.getNumber(str);
		
		System.out.println("result = " + result) ;
	}
	
	public static int getNumber(String str){
		int result = 0;
		int mulfactor = 1;
		int counter = 1;		
		
		for(int i=str.length()-1; i>=0; i--){
			String digitStr = String.valueOf(str.charAt(i));
			
			if(i !=  str.length()-1){			  
			  mulfactor = mulfactor * 10;
			}
			
			System.out.print("mulfactor = " + mulfactor);
			System.out.print("; digit = " + getDigitFromMap(digitStr));
			
			result +=  MathDemo1.getDigitFromMap(digitStr) * mulfactor;
			System.out.print("; result = " + result + "\n");			
		}
		
		return result;
	}
	
	public static int getDigitFromMap(String key){
		Map<String,Integer> map = new HashMap<String,Integer>();
		
		map.put("0",0);
		map.put("1",1);
		map.put("2",2);
		map.put("3",3);
		map.put("4",4);
		map.put("5",5);
		map.put("6",6);
		map.put("7",7);
		map.put("8",8);
		map.put("9",9);
		
		if(map.containsKey(key)){
			return (int)map.get(key);
		} else {
			return 0;
		}
	}
}

Thanks - Hitesh

[Hitesh Patel Patel]

I forget to add that a program should not use any in-build java function.

[fred rosenberger]

Then you are pretty much out of luck. length() is a build it function. print() is a build in function. toString (which you are implicitly calling with your string concatenation) is built in.

[Hitesh Patel Patel]

Sorry Fred I meant to say any in-build function that allows conversation from string to int or float.
Thanks for pointing it out.

[Henry Wong]

When you ran you program, did it work? I recommend trying it with small numbers first -- single digit, then two digit, etc. -- to see what you are doing wrong.

Henry