示例

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

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

}
解决方案 确保对象 c 是 Map
示例

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

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

}

}