Java-Code

import java.util.*;

public class NatZahl {
	public static void main(String [] args){

		System.out.print((long)f(99) + ( " (dezimal) "));
		
	}
	
	public static double f(int n){
		String Stringarray[] = new String[n];
		
		for(int i = n; i > 0; i--){
			if(i == n){
				System.out.print("f(" + n + ") => " + i + ", ");
			}
		else if(i != 1 && i < n){
			System.out.print(i + ", ");
			} 
		else{
				System.out.print(i + " => ");
			}
		}
		
		for(int i = n; i > 0; i--){
				Stringarray[i-1] = Integer.toBinaryString(i);
				if(i != 1){
				System.out.print(Stringarray[i-1] + ", ");
				}
				else{
					System.out.print(Stringarray[i-1] + " => ");
				}
		}
		
		List<String> help = new LinkedList<>();
	     for(int i = n; i > 0; i--){
	    	 help.add(Stringarray[i-1]);
	     }
	     String binarywo = String.join("", help);
	     System.out.print(binarywo + " = ");
	     double erg = binToDec(binarywo);

	   
		return erg;
	}
	 public static double binToDec(String bin) {
    	 double dec = 0L;
    	     double pow = 1;
    	     for (int i = (bin.length() - 1); i >= 0; i--) {
    	         char c = bin.charAt(i);
    	         dec = dec + (Double.parseDouble(c + "") * pow);
    	         pow = pow * 2;
    	     }
    	     return dec;
    	 }
}

Java-Code

import java.math.BigInteger;

public class Funktion {

	public static void main(String[] args) {
		// Schritt 1+2
		int fn = 12;
		String s = "";
		for (int j = 1; j <= fn; j++) {
			s = Integer.toBinaryString(j) + s;
		}

		//Schritt 3
		BigInteger res = BigInteger.ZERO;
		BigInteger ex = BigInteger.ONE;
		int oneORzero = -1;
		while (!s.equals("")) {
			oneORzero = Integer.valueOf(s.substring(s.length() - 1));
			if (oneORzero == 1) {
				res = res.add(ex);
			}
			ex = ex.shiftLeft(1);
			s = s.substring(0, s.length() - 1);
		}
		System.out.println(res);

	}
}

Java-Code

import java.math.BigInteger;

class natuerlicheZahl
{
    public static void main (String[] args) 
    {
        String f = "";
        int n = 99;
        for(int i = n; i > 0; i--) 
        {
            f = f.concat(Integer.toBinaryString(i));
        }
        BigInteger dezimal = new BigInteger(f, 2); 
        
        System.out.println("f: " + f);
        System.out.println("Dezimal: " + dezimal);        
    }
}