欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  IT编程

15道非常经典的Java面试题 附详细答案

程序员文章站 2024-03-12 08:33:32
试题如下: 参考答案: import java.io.filenotfoundexception; import java.io.ioex...

试题如下:

15道非常经典的Java面试题 附详细答案

15道非常经典的Java面试题 附详细答案

15道非常经典的Java面试题 附详细答案

15道非常经典的Java面试题 附详细答案

15道非常经典的Java面试题 附详细答案

参考答案:

import java.io.filenotfoundexception;
import java.io.ioexception;
import java.util.arraylist;
import java.util.concurrent.executorservice;
import java.util.concurrent.executors;

/**
 * created by ysc on 7/26/16.
 */
public class interview {
 private static void one(){
 string str1 = "hello";
 string str2 = "he"+new string("llo");
 system.err.println(str1==str2);
 system.out.println("1. false");
 }
 private static void two(){
 int i = integer.max_value;
 system.err.println((i+1)<i);
 system.out.println("2. 存在一个i, 使得(i+1)<i");
 }
 private static void three(){
 system.err.println("gc is not a java thread, it is a native thread");
 thread.getallstacktraces().keyset().foreach(thread -> system.out.println(thread.getname()+"->"+thread.isdaemon()+" "+thread.getpriority()));
 system.out.println("3. gc线程是daemon线程");
 }
 private static volatile int count = 0;
 private static void four(){
 executorservice executorservice = executors.newcachedthreadpool();
 for(int j=0; j<10; j++){
  executorservice.submit(()->{
  for(int i=0; i<1000000; i++){
   count++;
  }
  });
 }
 system.out.println("count should be: "+10000000+", actual be: "+count);
 system.out.println("4. volatile不能保证线程安全");
 }
 private static void five(){
 arraylist<integer> list = new arraylist<>(20);
 list.add(1);
 system.out.println("debug code, not execute grow method");
 system.out.println("5. list grow 0 times");
 }
 private static void six() {
 system.out.println("bufferedreader's constructor only accepts a reader instance");
 system.out.println("6. new bufferedreader(new fileinputstream(\"a.dat\")); is wrong");
 }
 private static void seven() {
 try{
  if(true){
  throw new ioexception();
  }
 }catch (filenotfoundexception e){
  system.out.print("filenotfoundexception!");
 }catch (ioexception e){
  system.out.print("ioexception!");
 }catch (exception e){
  system.out.print("exception!");
 }
 system.out.println("\n7. ioexception!");
 }
 private static void eight() {
 system.out.println("string s;system.out.println(s); error: variable s might not have been initialized\nrecompile with -xlint:unchecked for details.");
 system.out.println("8. 由于string s没有初始化, 代码不能编译通过");
 }
 private static void nine() {
 system.out.println("5"+2);
 system.out.println("9. 52");
 }
 private static void ten() {
 int i = 2;
 int result = 0;
 switch(i){
  case 1:
  result = result + i;
  case 2:
  result = result + i * 2;
  case 3:
  result = result + i * 3;
 }
 system.out.println("result="+result);
 system.out.println("10. 10");
 }
 private static class null{
 public static void hello(){
  system.out.println("hello");
 }
 public static void main(string[] args) {
  ((null)null).hello();
  null _null = (null)null;
  _null.hello();
 }
 }
 private static class stringexample1{
 string str = new string("good");
 char[] ch = {'a', 'b', 'c'};
 public void change(string str, char[] ch){
  str = "test ok";
  ch[0] = 'g';
 }

 public static void main(string[] args) {
  stringexample1 ex = new stringexample1();
  ex.change(ex.str, ex.ch);
  system.out.print(ex.str+" and ");
  system.out.print(ex.ch);
  system.out.println();
 }
 }
 private static class stringexample2{
 public static void change(string str){
  str = "welcome";
 }

 public static void main(string[] args) {
  string str = "1234";
  change(str);
  system.out.println(str);
 }
 }
 private static class forloop{
 static boolean foo(char c){
  system.out.print(c);
  return true;
 }

 public static void main(string[] args) {
  int i=0;
  for(foo('a');foo('b')&&(i<2);foo('c')){
  i++;
  foo('d');
  }
  system.out.println();
 }
 }
 private static class helloa{
 public helloa(){
  system.out.println("helloa");
 }

 { system.out.println("i'm a class"); }

 static {
  system.out.println("static a");
 }
 }
 private static class hellob extends helloa{
 public hellob(){
  system.out.println("hellob");
 }

 { system.out.println("i'm b class"); }

 static {
  system.out.println("static b");
 }

 public static void main(string[] args) {
  system.out.println("main start");
  new hellob();
  new hellob();
  system.out.println("main end");
 }
 }
 public static void main(string[] args) {
 one();
 two();
 three();
 four();
 five();
 six();
 seven();
 eight();
 nine();
 ten();
 null.main(null);
 stringexample1.main(null);
 stringexample2.main(null);
 forloop.main(null);
 hellob.main(null);
 }
}

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持。