Append a int variable to a StringBuffer

Question

I have this code

String str1 = (String) optionlist1.get(i);//str1=apple
String str2 = (String) optionlist2.get(i);//str2=mango
String str3 = (String) optionlist3.get(i);//str3=water

for(int k=1;k<4;k++){
   String str="str"+k;
   sb.append("<p>"+k+")"+str+"</p>");
}

When I print this I just get str1,str2,str3 instead of the actual data i.e apple,mango,water.

Is there a way to do this ? Let me know if more info is required.

Answer 1

That will not work since you are stating that str = "str" + k, which means that str will have values of str1, str2, etc. These values represent string literals, and not variable names. To go round your problem you can do this:

List<String> fruit = new ArrayList<String>();
fruit.add((String) optionlist1.get(i));
fruit.add((String) optionlist2.get(i));
fruit.add((String) optionlist3.get(i));

for(String str : fruit)
{
    System.out.println(str);
}

What you are trying to achieve is possible through the Reflection API (more on that here), however I think that for your particular problem, using reflection might be a little bit overkill, so it might be better to stick with the easier solutions.

EDIT: This code should do what you are after through the use of reflection:

    public static List<String> lst0 = new ArrayList<String>();
    public static List<String> lst1 = new ArrayList<String>();

    public static void main(String[] args) throws NoSuchElementException, NoSuchFieldException, IllegalAccessException
    {

       lst0.add("abc");       
       lst1.add("def");

       Class thisClass = SOTest.class;
       for(int i = 0; i < 2; i++)
       {
           Field field = thisClass.getField("lst" + i);
           List<String> lst = (List<String>) field.get(new ArrayList<String>());
           System.out.println(lst.get(0));
       }
    }

Answer 2

you cannot reference variables using their string literal because string "str1" is not equal to reference variable str1. One alternate approach can be to use an array as mentioned here:

    String strArrr[] = new String[3];

    String strArrr[0] = (String) optionlist1.get(i);//str1=apple
    String strArrr[1] = (String) optionlist2.get(i);//str2=mango
    String strArrr[2] = (String) optionlist3.get(i);//str3=water


    for(int k=1;k<4;k++){
    String str=strArr[k-1];
    sb.append("<p>"+k+")"+str+"</p>");
    }

Answer 3

A String by the name of str1 is not the same as a String with the value of str1

e.g.

  String str1 = "Apple";

  str1.equals ("str1") == false;

try using an array

String str[] = new String [3];
str[0] = (String) optionlist1.get(i);//str1=apple
str[1] = (String) optionlist2.get(i);//str2=mango
str[2] = (String) optionlist3.get(i);//str3=water

and then

for(int k=1;k<4;k++){
    String s=str[k-1];
    sb.append("<p>"+k+")"+s+"</p>");
}

Answer 4

Variable names cannot generate Dynamically.

You could try,

List<String> list = new ArrayList<String>();
list.add((String) optionlist1.get(i));//str1=apple
list.add((String) optionlist2.get(i));//str2=mango
list.add((String) optionlist3.get(i));//str3=water

int counter=1;
for(String str : list){
sb.append("<p>"+counter+")"+str+"</p>");
counter++;
}

Answer 5

str1, str2 and str3 are variable names. You are creating variable names as a String str = "str" + k which is ultimately a value not variable name.

You need to create an array of String to store your options.

String[] strs = new String[];

You can add your str1, str2.. to this array.

strs[0] = str1; strs[1] = str2; strs[2] = str3;

and access this array in your for loop.

for(int k=0; k < 3; k++) { 
    String str="str"+k;
    sb.append("<p>"+ strs[k] + "</p>");
}

This will work. :)