String Replace Program in Java

public class Replace{
    public static void main(String s[]){
        String string="rajesh raju raja rahul ray rani ram";
        char  oldChar='r';
        char newChar='g';
        int numChar=string.length();
        char[] charArray=new char[numChar];
        string.getChars(0, numChar, charArray,0);
        int i=0,flag=0;
        System.out.println("Your String before repalce\n"+string);
        while(i<charArray.length)
        {
        if(charArray[i]==oldChar)
            {
            charArray[i]=newChar;
            flag=1;
            }
        i++;
        }
        if(flag==1)
            {
            System.out.println("\nYour String after repalceing 'h' with 'j'");
            String newString=new String(charArray);
            System.out.println(newString+"\n\nYour char has been replaced");
            }
        if(flag==0)
            {
            System.out.println("\nThe char not found");
            }
    }
}