Unnecessary Cast in Map

Unnecessary casts clog your code and slow down you applications. They may seem small individually, but if they are inside loops or frequent code paths, they do add up. One common unnecessary cast happens to java.util.Map key:

public static void unnecessaryCast() {

Map map = new HashMap();
map.put("language", "Java");

for(Iterator it = map.keySet().iterator(); it.hasNext();) {
    //casting key to String is unnecessary for map lookup
    String key = (String) it.next();
 
    //casting to String is unnecessary for println
    String val = (String) map.get(key);
 
    System.out.println("key = " + key + ", value = " + val);
}
}

Casting (in red) for the map key is not needed for the purpose of calling java.util.Map.get(key), unless you also need a String type of key later.

Casting (in blue) for the map value is not needed for the purpose of System.out.println(value), unless you also need a String type of value later. JVM will correctly dispatch to String.toString() when you concatenate ", value = " to an java.lang.Object value.

So I would simply change the two lines to:

Object key = it.next();
    Object val = map.get(key);

Tags: Java, Java Language, Java Cast