javaOCP1~20

Given the code fragment: String s1 = new string ("ORACLE"); String s2 = s1. intern(); String s3 ="ORACLE"; System.out.print((s1==s2)+""); System. out.print ((s1 ==s3)+""); System. out. printIn(s2 ==s3); 结果如何?

/ /Line 1

public class Computator <N extends Number, c extends Collection<N>>{

public N sum (c collection){ / /Line 2

double sum =0.0; / /Line 3

for(N collection){ // Line 4

 sum + =n. doublevalue();

}

return sum;

}

public static void main (string... args){

var numbers=list.of(5,4,6,3,7,2,8,1,9);//Line 5

Computator<Integer,List<Integer>>c=new Computator<>();

System.out. printIn(c. sum(numbers));

 }

}

哪个操作使计算机类能够编译?

public class Person {

 private string name ="Green";

 public void setName(String name){

 String title="mr."

 name= title+name;

 }

 public String tostring () {

 return name;

 }

}

and

public class Test {

 public static void main( String args[]) {

 Person P = new Person();

 p. setName ("Blue");

 System.out. printIn(p);

 }

}

结果如何?

public class CustomException extends Exception {

 private final int errorcode;

 public CustomException(int errorcode, Throwable cause){

 super(cause);

 this. errorCode = errorcode;

}

public CustomException(int errorCode, String message,

Throwable cause){

super(message, cause);

this. errorcode = errorcode;

}

public string getMessage （）{

 return string. format ("Code: &d - &s [8s]", this. errorCode,

 super. getMessage(),

 this.getcause().getMessage()):

}

public static void main(String [ ] args){

try {

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

 new FileNotFoundException ("MyFile. txt") ) // Line 1

} catch(CustomException ex){

system.out.printIn(ex.getMessage( ) );

 }

 }

}

结果如何?

public class Main{

public static void main(string [ ]args) {

try{

Path source = Paths. get ("/u01/work/stage/message. txt");

Path target = Paths. get ("/u01/work/merge. txt");

Files. copy(source, target, standardcopyOption. REPLACE_EXISTING.;

BasicFileAttributes attr = Files. readAttributes(target,BasicFileAttributes.class);

 System.out print(attr. isRegulaFile());

} catch (IOException e){

 e.printStackTrace();

}

}

}

哪个是正确答案？

class classes implements Serializable {

 string id;

}

class Person{

 string name;

 transient string address;

}

class Student extends Person implements Serializable {

String studentNo;

Classes classes = new classes ();

Student对象中哪些字段是序列化的?

public class Tester {

 public static void main(string [ ] args){

 float x =2, y=3, z =4;

 float a =y % x, b = z % y;

 if (a > b){

 System.out.printIn (a + b);

 }

 }

}

import java.util.List;

import java.util. Optional;

public class Test {

 public static void main (String[ ] args) {

 var items = List. of (new Item("A", 10), new Item ("B", 2),

 new Item ("C", 12), new Item("D", 5),

 new Item ("E", 6));

double avg =items. stream(). mapToInt (i -> i. amount). average () .orElse (0 .0);

Optional<Item>item= items. parallelstream( )

 .filter(i->i. amount< avg). findAny();

System.out. println (item. orElseThrow ( ));

}

class Item {

public string name; public int amount;

public Item (String name, int amount){

 this. name = name; this. amount =amount;

}

@override

public string toString( ) ( return"Name:"+name+", Amount+ amount;)

}

哪个是正确答案？

public interface Rectangle{

 default double calculateSurfaceArea(double 1, double w){

 return 1 * w;

 }

}

public interface Ellipse {

 default double calculateSurfaceArea(double majorR, double minorR){

 return Math.PI * majorR* minorR;

 }

}

public class Cylinder implements Rectangle, Ellipse {

 public double calculateSurfaceArea(double 1, double w, double majorR, double

minorR){

 double rectArea= Rectangl. super.calculateSurfaceArea(1,w);

 double ellipseArea = Ellipse. super. calculateSurfaceArea(majorR, minorR);

 return rectArea + ellipseArea * 2;

 }

}

是什么阻止了代码的编译?

on new feature

for mlib. jar, you see that the customer visible method

public void enableservice(String hostName, string portNumber)

executes this code fragment

try { 

AccessController. doPrivileged ((PrivilegedExceptionAction<Void>)()->{

transportSocket = new Socket (hostName, portNumber);

return null;

});

}

and you see that this grant is in the security policy file:

grant codebase "file:$(mlib home)/j2se/home/mlib. jar"{

permission java.io. SocketPermission "*", "connect";

};

这会给云客户的代码带来哪些安全漏洞?

public class Tester {

public static int reduce (int x){

int y=4;

class Computer{

int reduce(int x){

return x-y--;

}

}

Computer a= new Computer();

return a. reduce(x);

}

public static void main (String[ ] args){

System. out. print (reduce (1));

}

}

结果如何?

Given: import java.util.*; public class Foo { public List<Integer> foo(Set<CharSequence> m) {...} } and import java.util.*; public class Bar extends Foo { //line n1 } 在Bar类编译的第n1行有哪两个方法定义?

Given this code fragment: public void foo (Function<Integer, String> fun){...} 哪两个选项能正确编译?

Stream<Integer>data=Intstream. range(1,10000). boxed();

Integer sum=data. mapToInt(a->a).sum( ); //line 1

哪两个代码片段独立地替换第一行来实现等价的reduce操作?  

@Repeatable (Meals. class)

@Target (ElementType. TYPE.

@interface Meal {

 string starter () default "";

 string maincourse();

 String dessert( ) default "";

}

and

@Target(ElementType. TYPE.

public @interface Meals {

Meal [ ] value ();

}

哪两个是注释的有效用法?

package com. foo;

public class Foo{

static final int A = 0;

public static final int B =0;

private static final int C= 0;

int d=0;

protected int e =0;

public int f=0;

private int g =0;

public void foo (int h){

int i=0;

 }

}

and

package com. foo. bar;

public class Bar extends com. foo. Foo{

@override

public void foo (int j){

 //line 1

 }

} 

Foo和Bar类中的哪四个标识符在第一行可见?