when we use return statement inside if block why compiler not giving any error?

Question

Can anyone help me to understand why java compiler not giving any error for code 1. As in code 1, there is no chance of executing line 2 at run-time. is compiler not validating if condition ? And why it is giving error on code 2.

Code 1 :

public class HelloWorld{

     public static void main(String []args){
        m1();
     }
     
     public static String m1() {
         if(true){
             System.out.println("if");
             return ""; //line 1
         } else {
             System.out.println("else"); // line 2
             return "";
         }
     }
}

Code 2 :

public class HelloWorld{

     public static void main(String []args){
        m1();
     }
     
     public static String m1() {
         return "";
         System.out.println("last statement"); //compile error : unreachable statement
     }
     
}