範例

public class ClassA {
Collection c;
Map m;
public void methodA() {

m = (Map) c;
// ...
}

}
解決方案 請確定 c 物件是一個 Map
範例

public class ClassA {
Collection c;
Map m;
public void methodA() {

if (c isntanceof Map){
m = (Map) c;
// ...

}

}