1.==和equals()

public class StrEqu {
    public static void main(String[] args) {
        String str1="bdqn";
        String str2="bdqn";
        System.out.println(str1==str2);
        System.out.println(str1.equals(str2));
        
        String str3=new String("bdqn");
        System.out.println(str1==str3);
        System.out.println(str1.equals(str3));
        
        String str4=new String("bdqn");
        System.out.println(str3==str4);
        System.out.println(str3.equals(str4));
    }
}