use std::collections::HashMap;
let dic = HashMap::from([
(1, "A"), (2, "B")
]);
let value1 = dic.get(&3);
//value1 is None
let value2 = dic.get(&3)
.cloned().unwrap_or("-");
//value2 is "-"
println!("value1 is {:?}", value1);
println!("value2 is {:?}", value2);