SCJP刷题学习笔记（Part thirteen）

QUESTION 121

Given:

class MyClass implements AutoCloseable {
int test;
public void close() {}
public MyClass copyObject() {return this;}
}

 

and the code fragment:

		MyClass obj=null;
		try(MyClass obj1 =new MyClass())
		{
			obj1.test=100;
			obj=obj1.copyObject();		//line n1
		}
		System.out.println(obj.test);	//line n2

 

What is the result?

A. An exception is thrown at line n2 .

B. 100

C. A compilation error occurs because the try block is declared without a catch or finally block.

D. A compilation error occurs at line n1 .

Correct Answer: B

Section: (none)

Explanation

Explanation/Reference:

 

 

 

QUESTION 122

Which two methods from the java.util.stream.Stream interface perform a reduction operation?

(Choose two.)

A. count ()

B. collect ()

C. distinct ()

D. peek ()

E. filter ()

Correct Answer: AB

Section: (none)

Explanation

Explanation/Reference:

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/stream/package-summary.html

 

 

 

QUESTION 123

Which code fragment is required to load a JDBC 3.0 driver?

A. Connection con = Connection.getDriver

(“jdbc:xyzdata://localhost:3306/EmployeeDB”);

B. Class.forName(“org.xyzdata.jdbc.NetworkDriver”);

C. Connection con = DriverManager.getConnection

(“jdbc:xyzdata://localhost:3306/EmployeeDB”);

D. DriverManager.loadDriver (“org.xyzdata.jdbc.NetworkDriver”);

Correct Answer: B

Section: (none)

Explanation

Explanation/Reference:

 

 

 

QUESTION 124

Given:

public class Foo<K,V>{
	private K key;
	private V value;
	
	public Foo(K key,V value) {this.key=key;this.value=value;}
	public static<T> Foo<T,T> twice(T value){
		return new Foo<T,T>(value,value);
	}
	public K getKey() {return key;}
	public V getValue() {return value;}

}

 

Which option fails?

A. Foo<String, Integer> mark = new Foo<String, Integer> (“Steve”, 100);

B. Foo<String, String> pair = Foo.<String>twice (“Hello World!”);

C. Foo<Object, Object> percentage = new Foo<String, Integer>(“Steve”, 100);

D. Foo<String, String> grade = new Foo <> (“John”, “A”);

Correct Answer: A

Section: (none)

Explanation

Explanation/Reference:

 

 

 

QUESTION 125

Given the code fragment:

		List<Integer>prices =Arrays.asList(3,4,5);
		prices.stream()
		.filter(e->e>4)
		.peek(e->System.out.print("Price"+e))			//line n1
		.map(n->n-1)									//line n2
		.peek(n->System.out.println("New Price"+n));	//line n3

 

Which modification enables the code to print Price 5 New Price 4 ?

A. Replace line n2 with .map (n -> System.out.println (“New Price” + n –1)) and

remove line n3

B. Replace line n2 with .mapToInt (n -> n – 1);

C. Replace line n1 with .forEach (e -> System.out.print (“Price” + e))

D. Replace line n3 with .forEach (n -> System.out.println (“New Price” + n));

Correct Answer: D

Section: (none)

Explanation

Explanation/Reference:

 

 

 

QUESTION 126

Given the definition of the Book class:

public class Book {
	private int id;
	private String name;
	public Book(int  id,String name) {
		this.id=id;
		this.name=name;
	}
	public int getId() {return id;}
	public String getName() {return name;}
	public void setId(int id) {this.id=id;}
	public void setName(String name) {this.name=name;}
}

 

Which statement is true about the Book class?

A. It demonstrates encapsulation.

B. It is defined using the factory design pattern.

C. It is defined using the singleton design pattern.

D. It demonstrates polymorphism.

E. It is an immutable class.

Correct Answer: A

Section: (none)

Explanation Explanation/Reference:

 

 

 

QUESTION 127

Given the code fragment:

ProductCode<Number,Integer> c1=new ProductCode<Number, Integer>();//c1 instantiation
ProductCode<Number,String> c2= new ProductCode<Number,String>();//c2 instantiation

 

You have been asked to define the ProductCode class. The definition of the ProductCode class must

allow c1 instantiation to succeed and cause a compilation error on c2 instantiation.

Which definition of ProductCode meets the requirement?

Correct Answer: B

Section: (none)

Explanation

Explanation/Reference:

 

 

 

QUESTION 128

Given the code fragment:

Map<Integer,Integer> mVal=new HashMap<>();
		mVal.put(1,10);
		mVal.put(2,20);
		//line n1
		c.accept(1,2);
		mVal.forEach(c);

 

Which statement can be inserted into line n1 to print 1,2; 1,10; 2,20; ?

A. BiConsumer<Integer,Integer> c = (i, j) -> {System.out.print (i + “,” + j+

“; “);};

B. BiFunction<Integer, Integer, String> c = (i, j) –> {System.out.print (i + “,”

+ j+ “; “)};

C. BiConsumer<Integer, Integer, String> c = (i, j) –> {System.out.print (i + “,”

+ j+ “; “)};

D. BiConsumer<Integer, Integer, Integer> c = (i, j) –> {System.out.print (i +

“,” + j+ “; “);};

Correct Answer: A

Section: (none)

Explanation

Explanation/Reference:

Reference: https://www.concretepage.com/java/jdk-8/java-8-biconsumer-bifunction-bipredicate-example

BiConsumer接口说明: https://blog.youkuaiyun.com/qq_28410283/article/details/80704487

 

 

 

QUESTION 129

Given the code fragment:

        List<String>nums=Arrays.asList("EE","SE");
		String ans =nums
				.parallelStream()
				.reduce("Java ", (a,b)->a.concat(b));
		System.out.print(ans);

 

What is the result?

A. Java EEJava EESE

B. Java EESE

C. The program prints either:

Java EEJava SE

or

Java SEJava EE

D. Java EEJava SE

Correct Answer: D

Section: (none)

Explanation

Explanation/Reference:

 

 

 

QUESTION 130

Given the code fragments :

public class Product {
	String name;
	Integer price;
	Product(String name,Integer price){
		this.name=name;
		this.price=price;
	}
	public void printVal() {
		System.out.print(name+"Price:"+price+"");
	}
	public void setPrice(int price) {this.price=price;}
	public Integer getPrice() {return price;}
}

 

and

List<Product> li= Arrays.asList(new Product("TV",1000),new Product("Refrigerato",2000));
Consumer<Product> raise=e->e.setPrice(e.getPrice()+100);
li.forEach(raise);
li.stream().forEach(Product::printVal);

 

What is the result?

A. TV Price :1100 Refrigerator Price :2100

B. A compilation error occurs.

C. TV Price :1000 Refrigerator Price :2000

D. The program prints nothing.

Correct Answer: A

Section: (none)

Explanation

Explanation/Reference: