Why is wrong with my code???

import java.io.*;

public class fs
{
    public static void main(String args[]) throws IOException
    {
        String [] datatype = new String[4];//{"boolean","byte","char","double","float","int","long","short"};
        String input;
        //int i=0;
        BufferedReader buff = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter String: ");
        input = buff.readLine();
        
        datatype[0]="boolean";
        datatype[1]="byte";
        datatype[2]="char";
        datatype[3]="double";
        
        
        for(int i=0;i<datatype.length;i++)
        {
            if(input==datatype[i])
            {
                System.out.println("WORD FOUND");
                i=datatype.length;
            }
            else
            {
                System.out.println("WORD NOT FOUND");
            }
        }
    }
}