标题: 报空指针异常，是为什么？请告诉实际发生的原理 [打印本页] 作者: 羽狼之翼 时间: 2015-1-28 21:34 标题: 报空指针异常，是为什么？请告诉实际发生的原理 public class Demo4 {
public static void main(String[] args) {
Map<String, Student> map = new TreeMap<String, Student>(new Comparator<String>()
{
@Override
public int compare(String s1, String s2) {
return -1;
}
});
map.put("abc", new Student("1", "11"));
map.put("bac", new Student("2", "22"));
map.put("cba", new Student("3", "33"));
map.put("cab", new Student("4", "44"));
map.put("b", new Student("5", "55"));
map.put("a", new Student("5", "55"));
map.put("bca", new Student("6", "66"));
Set<String> set = map.keySet();
for (String key : set) {
Student s = map.get(key);
System.out.println(s.getName() + "***" + s.getId());
}
}
}
public class Student {
private String id;
private String name;