Question

线程“ main”中的异常java.lang.ClassCastException： setcollection.Enseignant无法转换为java.lang.Comparable

public class Test {

    /**
    * @param args the command line arguments
    */
    public static void main(String[] args) {
        Enseignant e=new Enseignant();
        Enseignant e1=new Enseignant(1,"bargaoui","haythem");
        Enseignant e2=new Enseignant(12,"islem","ben ahmed");
        System.out.println(e1.toString());
        System.out.println(e2.toString());
        System.out.println(e1.equals(e2));
        TreeSet<Enseignant> treeset = new TreeSet<Enseignant>(); 
        Enseignant E1=new Enseignant(1,"mohamed","ben brahim");
        Enseignant E2=new Enseignant(2,"imed","rouabi");
        Enseignant E3=new Enseignant(3,"salim","ali");
        Enseignant E4=new Enseignant(4,"zayneb","sassi");
        Enseignant E5=new Enseignant(5,"khalid","louati");
        Enseignant E6=new Enseignant(6,"hatem"," himadi");


        treeset.add(E1);
        treeset.add(E2);
        treeset.add(E3);
        treeset.add(E4);
        treeset.add(E5);
        treeset.add(E6);
        System.out.println(treeset.contains(E4));
        System.out.println(treeset.contains(E1.getId()));
        System.out.println(treeset.remove(E6));
        Iterator iterator = treeset.iterator();

        // afficher tous les éléments de TreeSet
        System.out.println("éléments de TreeSet");     
        while (iterator.hasNext()){
        System.out.println(iterator.next());
        }
    }
}

线程“ main”中的异常java.lang.ClassCastException：

Answer 1

由于您使用的是TreeSet，将进行一些比较，并且需要Comparator <>。

您可以做两件事。

实施中可比性<>

public class Enseignant implements Comparable<Enseignant> {
...
  public int compareTo(Enseignant other) {
    // Compare here
    return 0;
  }
...
}

在创建TreeSet时添加比较器

TreeSet<Enseignant> treeset = new TreeSet<>(new Comparator<Enseignant>(){
  public int compare(Enseignant e1, Enseignant e2) {
    // Compare here.
    return 0;
  }
});

线程“主”中的异常java.lang.ClassCastException：setcollection.Enseignant无法转换为java.lang.Comparable

1 个答案: