15-Way Very classic Java face questions with detailed answers _java

The questions are as follows:

Reference Answer:

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").
 There is an I, which makes (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 thread is a daemon thread ");
 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 is: "+count);" System.out.println ("4").
 Volatile cannot guarantee thread safety ");
 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 ' 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").
 Because string s is not initialized, the code cannot be compiled through ");
 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 ();
 The 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);
  The 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 ();
 The 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);
 }
}

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