CODEWITHSUNDEEP
javacastingarraylist
user2042521
user2042521

Reputation: 45

Java cast of ArrayList<Map>

sorry to say, I'm not very experienced with Java. I'm using eclipse as IDE. Eclispe complains about unchecked cast which I can not understand. Please refer to the code snipet. How to make this right in general ?

public Liberty2Server(ArrayList<Map<String,String>> libertySourceFiles , String basePath) throws FileNotFoundException , IllegalArgumentException {
    // check input file path
    for( Object map : libertySourceFiles) {
        Map<String,String> mp = (Map<String,String>) map ;  // <==Eclipse complains here: Unchecked cast from Object to Map<String,String>

Any hint is welcome

Rolf

Upvotes: 0

Views: 191

Answers (4)

Carlo Pellegrini
Carlo Pellegrini

Reputation: 5686

The problem here is that you upcast the ArrayList<Map<String,String>> element do Object and then downcast it to a generic type. The solution is easy:

public Liberty2Server(ArrayList<Map<String,String>> libertySourceFiles , String basePath) throws FileNotFoundException , IllegalArgumentException {
    // check input file path
    for(  Map<String,String> mp : libertySourceFiles) {
      //  Map<String,String> mp = (Map<String,String>) map ; Not needed anymore
      ....

Upvotes: 0

Joshua
Joshua

Reputation: 2982

Eclipse complains, because you want to cast an Object to a Map<String, String>. Change the type of your running variable map to Map<String, String>, and everything will be fine. You won't even need the variable mpthen.

Upvotes: 0

Peter Lawrey
Peter Lawrey

Reputation: 533492

It means you are performing a cast which the compiler cannot check is safe.

It warns you that you have to check it's safe.

A better solution is to remove the need for the cast by using

for(Map<String, String> mp : libertySourceFiles) {

Upvotes: 2

assylias
assylias

Reputation: 328598

You can change your for loop and use the explicit type in the collection:

for(Map<String,String> map : libertySourceFiles) {
    Map<String,String> mp = map; //probably not needed any more
}

Upvotes: 3

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