public class Main{

public static void main(String[] args){

Optional<String> value=createValue();

String str=value.orElse("Duke");

System.out.println(str);

}

static Optional<String> createValue(){

String s=null;

return Optional.ofNullable(s);

}

}

输出是什么?

var fruits=List.of("apple","orange","banana","lemon");

Optional<String> result=fruits.stream()

.filter(f->f.contains("n"))

.findAny(); //line 1

you replace the code on line 1 to use ParalledStream

哪一个是正确的?

import java.util.fucntion.BiFunction;

public class Pair<T>{

final BiFunction<T,T,Boolean> validator;

T left =null;

T right=null;

private Pair(){

validator=null;

}

Pair(BiFunction<T,T,Boolean> v,T x,T y){

validator=v;

set(x,y);

}

void set(T x,T y){

if(!validator.apply(x,y)) throw new IllegalArgumentException();

setLeft(x);

setRight(y);

}

void setLeft(T x){

left=x;

}

void setRight(T y){

right=y;

}

final boolean isValid(){

return validator.apply(left,right);

}

}

如果需要p instanceof Pair则p. isvalid()返回true, 确保满足此需求的最小可见性更改集合是什么? （答案有争议）

public class Main{

public static void main(String[] args){

List<String> fruits =List.of("banana","orange","apple","lemon");

Stream<String> s1=fruits.stream();

Stream<String> s2=s1.peek(i->System.out.print(i+" "));

System.out.println("-----");

Stream<String> s3=s2.sorted();

Stream<String> s4=s3.peek(i->System.out.print(i+" "));

System.out.println("-----");

String strFruits=s4.collect(Collectors.joining(","));

}

}

输出是什么?

class Super{

final int num; //line 1

public Super(int num){

this.num=num;

}

final void method(){

System.out.println("Output from super");

}

}

class Sub extends Super{

int num;//line n2

Sub(short num){ //line n3

super(num);

}

protected void method(){ //line 4

System.out.println("Output from Sub");

}

}

哪行代码会导致编译错误?  

String[] words={"am","am","first","second","mismatch"};

Map<Object,Long> map=Arrays.stream(words).collect(Collectors).groupingBy(x-

>x,Collectors.counting()));

System.out.println(map);

考虑到元素的顺序是不可预测的，那么输出是什么呢?  

var i=0;

var result=IntStream.generate(()->{i++; return i*i;}).limit(100).sum();

哪个陈述产生了相同的结果?（答案有争议）

class Super{

static String greeting(){return "Good Night";}

String name(){ return "Harry";}

}

and

class Sub extends Super{

static String greeting(){ return "Good Morning";}

String name(){ return "Potter"; }

}

and

class Test{

public static void main(String[] args){

Super s=new Sub();

System.out.println(s.greeting()+", "+s.name());

}

}

结果如何?

import java.io.*;

public class Tester{

public static void main(String[] args){

try{

doA();

doB();

}catch(IOException e){

System.out.print("c");

return;

} finally{

System.out.print("d");

}

System.out.print("f");

}

}

private static void doA(){

System.out.print("a");

if(false){

throw new IndexOutOfBoundsException();

}

}

private static void doB() throws FileNotFoundException{

System.out.print("b");

if(true){

throw new FileNotFoundException();

}

}

结果如何?

public class ExSuper extends Exception{

private final int eCode;

public ExSuper(int eCode,Throwable cause){

super(cause);

this.eCode=eCode;

}

public ExSuper(int eCode,String msg,Throwable cause){

super(msg,cause);

this.eCode=eCode;

}

public String getMessage(){

return this.eCode+": "+super.getMessage()+"-"+this.getCause().getMessage();

}

}

public class ExSub extends ExSuper{

public ExSub(int eCode,String msg,Throwable cause){

super(eCode,msg,cause);

}

}

and the code fragment:

try{

String param1="Oracle";

if(param1.equalsIgnoreCase("oracle")){

throw new ExSub(9001,"APPLICATION ERROR-9001",new 

FileNotFoundException("MyFile.txt"));

}

throw new ExSuper(9001,new FileNotFoundException("MyFile.txt")); // Line 1

}catch(ExSuper ex){

System.out.println(ex.getMessage());

}

结果是什么?

char[] characters=new char[100];

try(FileReader reader=new FileReader("file_to_path");){

//lline 1

System.out.println(String.valueof(characters));

}catch(IOException e){

e.printStackTrace();

}

您希望通过读取器对象读取数据。  

插入到第1行中的哪个语句将完成这个操作?  

public class Tester{

public static void main(String[] args){

StringBuilder sb=new StringBuilder(5);

sb.append("HOWDY");

sb.insert(0,' ');

sb.replace(3,5,"LL");

sb.insert(6,"COW");

sb.delete(2,7);

System.out.println(sb.length());

}

}

结果如何?

public class Tester{

public static void main(String[] args){

int x=0,y=6;

for(;x<y;x++,y--){ //line 1

if(x%2==0){

continue;

}

System.out.println(x+"-"+y);

}

}

}

结果如何?

Path v1=Paths.get("/./forest/./").resolve(Paths.get("tree.txt"));

Path v2=new File("/forest/./water/../tree.txt").toPath();

System.out.print(Files.isSameFile(v1,v2));

System.out.print(" "+v1.equals(v2));

System.out.print(" "+v1.normalize().equals(v2.normalize()));

假设所有引用路径都在文件系统中，这是结果吗? （单选题答案有争议）

public enum Season{

WINTER('w'),SPRING('s'),SUMMER('h'),FALL('f');

char c;

private Season(char c){

this.c=c;

}

}

and the code fragment:

public static void main(String[] args){

Season[] sA=Season.values();

//line n1

}

哪三个代码片段在第n1行打印了SPRING?  

Path p1=Paths.get("/scratch/exam/topsecret/answers");

Path p2=Paths.get("/scratch/exam/answers/temp.txt");

Path p3=Paths.get("/scratch/answers/topsecret");

哪两个语句打印出 ..\..\answers\topsecret?