奇奇怪怪的面试题
下列存在死循环风险的是ABCD
有需要互关的小伙伴,关注一下,有关必回关,争取今年认证早日拿到博客专家
public static void main(String[] args) {
List<String> list = new ArrayList<>();
list.add("aa");
list.add("bb");
while (list.iterator().hasNext()){
System.out.println(list.iterator().next());
}
} public static void main(String[] args) {
List<String> list = new ArrayList<>();
list.add("aa");
list.add("bb");
while (list.iterator().hasNext()){
System.out.println(list.iterator().next());
}
}public static void main(String[] args) {
int count = 0;
while (count < 10) {
if (count == 4) {
continue;
}
System.out.println(count);
count++;
}
}public class Tmp {
private boolean flag = true;
public void setFlag(boolean flag) {
this.flag = flag;
}
public void fun() {
while (flag) {
}
System.out.println("done");
}
public static void main(String[] args) throws InterruptedException {
final Tmp flagTest = new Tmp();
new Thread(() -> flagTest.fun()).start();
Thread.sleep(200);
flagTest.setFlag(false);
}
}public Category findRoot(long categoryId) {
Category category = categoryMapper.findCategoryById(categoryId);
if(category == null) {
throw new BusinessException("分类不存在");
}
long parentId = category.getParentId();
if(parentId == null || parentId == 0) {
return category;
}
return findRoot(parentId);
}环形链表
两个线程并发执行下列代码，其中直接使用线程安全类ConcurrentHashMap的put方法时不需要考虑多线程间互相覆盖的问题。
private static void extracted() {
ConcurrentHashMap<String, Student> map = new ConcurrentHashMap<>();
String key = "test";
Student student = map.get(key);
if (student == null) {
student = new Student();
map.put(key, student);
}
}下列代码可以编译通过。
public static void main(String[] args) {
List<String> list = new ArrayList<>();
list.add("ab");
printList(list);
}
public static void printList(List<Object> list) {
Iterator it = list.iterator();
while (it.hasNext()) {
System.out.println(it.next());
}
}关于 hashCode 和 equals 的处理，下列哪些说法是正确的？ AC
A. 只要覆写equals，就必须覆写hashCode
B. Set存储的对象可以不用覆写hashCode 和 equals这两种方法
C. 如果自定义对象作为Map的键，那么必须覆写hashCode和equals
D. hashCode相等时，equals一定相等一般建议覆写equals就重写hashCode,
Set中存的对象为自定义对象时重写hashCode 和 equals这两种方法
如果自定义对象作为Map的键，那么最好覆写hashCode和equals
public class Tmp {
public static void main(String[] args) {
Student zs1 = new Student("zs");
Student zs2 = new Student("zs");
HashSet<Student> set = new HashSet<>();
set.add(zs1);
boolean addSuccess = set.add(zs2);
if (addSuccess) {
System.out.println("add 成功了");
}
Map<Student, Integer> map = new HashMap<>();
map.put(zs1, 1);
Integer put = map.put(zs2, 2);
if (put == null) {
System.out.println("put 成功了");
}
}
}
class Student {
String name;
public Student(String name) {
this.name = name;
}
}下面选项中，请找出BigDecimal创建方法存在精度风险的选项？
A. BigDecimal a = new BigDecimal(0.1F)
B. BigDecimal b = new BigDecimal("0.1")
C. BigDecimal c = BigDecimal.valueOf(0.1)会输出list 对
class A{
public void hello(List list){
System.out.println("list");
}
public void hello(ArrayList list){
System.out.println("arrayList");
}
public static void main(String[] args) {
A a = new A();
List list = new ArrayList();
a.hello(list);
extracted();
}
}输出false false T
private static void main(String[] args) {
double a = 1.0D - 0.9D;
double b = 0.1D;
Double x = Double.valueOf(a);
Double y = Double.valueOf(b);
System.out.println(a == b);
System.out.println(x.equals(y));
}输出 false 0 T
private static void main(String[] args) {
BigDecimal b1 = new BigDecimal("1.0");
BigDecimal b2 = new BigDecimal("1.00");
System.out.println(b1.equals(b2));
System.out.println(b1.compareTo(b2));
}输出 0 1 2 3 4 和UnsupportedOperationException异常
private static void main(String[] args) {
Integer[] arr = new Integer[5];
for (int i = 0; i < 5; i++) {
arr[i] = i;
}
List<Integer> list = Arrays.asList(arr);
arr[0] = 6;
for (Integer integer : list) {
System.out.println(integer);
}
list.add(7);
}输出false 和 true
用org.apache.commons.lang3包的StringUtils
private static void main(String[] args) {
String str = " ";
boolean empty = StringUtils.isEmpty(str);
System.out.println("empty = " + empty);
boolean blank = StringUtils.isBlank(str);
System.out.println("blank = " + blank);
}输出 NullPointerException
private static void extracted4() {
Boolean a = null;
Boolean b = true ? a : false;
System.out.println("b = " + b);
}输出true
private static void extracted5() {
List<String> list1 = new ArrayList<>();
list1.add("eee");
list1.add("www");
List<String> list2 = new LinkedList<>();
list2.add("eee");
list2.add("www");
System.out.println(list1.equals(list2));
}输出true
private static void extracted6() {
Set<String> set1 = new HashSet<>();
Set<String> set2 = new LinkedHashSet<>();
set1.add("www");
set2.add("www");
System.out.println(set1.equals(set2));
}输出true
private static void extracted7() {
Map<Integer, String> m1 = new TreeMap<>();
Map<Integer, String> m2 = new LinkedHashMap<>();
m1.put(1, "www");
m1.put(2, "eee");
m2.put(2, "eee");
m2.put(1, "www");
System.out.println(m1.equals(m2));
}输出false
private static void extracted8() {
Integer integer = new Integer(3);
System.out.println(integer.equals("3"));
}本文参与 腾讯云自媒体分享计划，分享自作者个人站点/博客。
原始发表：2024-03-10，如有侵权请联系 cloudcommunity@tencent.com 删除
评论
登录后参与评论
推荐阅读