javaOCP121~140

package a;

abstract class A{

 void print(){

 System.out.println("Base class");

 }

}

and

package a;

public class B extends A{

 protected void print(){

 System.out.println("Derived class");

 }

 public static void main(String[] args) {

 B b=new B();

 ((A.b).print();

 }

}

输出是什么?

StringBuilder s=new StringBuilder(“ABCD”);

什么会导致s是AQCD?

public class ConsoleTest {

 public static void main(String[] args) {

 Console console=System.console();

 var name=console.readLine("Input Name: ");

 var password=console.readPassword("Input Password: ");

 System.out.println("Name is: "+name+", Password 

is:"+String.valueOf(password));

 }

}

and the command:

java ConsoleTest

The user will input Duke and Java when the input is prompted

输出是什么?

public class Foo{

private void print(){

System.out.println(“Bonjour le monde”);

}

public void foo(){

print();

}

}

public class Bar extends Foo{

private void print(){

System.out.println(“Hello world”);

}

public void bar(){

print();

}

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

Bar b=new Bar();

b.foo();

b.bar();

}

}

输出是什么?

public class Test {

 public static void main(String[] args) {

 int number=20;

 Predicate<Integer> p=a->a%2!=0;

 //line 1

 System.out.println(number+" is odd.");

 } else {

 System.out.println(number+" is even.");

 }

 }

}

第1行中的哪条语句使Test类能够编译?   

5. IntStream str = IntStream.of(2,3,4);

6. IntFunction<Integer> func= x->y->x*y;

7. str.map(func.apply(10)).forEach(System.out::println);

哪些操作将使代码能够编译?

 private T value;

 public T getValue(){

 return value;

 }

 public void setValue(T value){

 this.value=value;

 }

}

and

public class Test {

 public static void main(String[] args) {

 MyType<String> strType=new MyType<>();

 MyType<? extends Number> type=new MyType<>();

 strType.setValue("test");

 type.setValue(null);

 System.out.println(strType.getValue()+":"+type.getValue());

 }

}

结果如何?

 private String name;

 public Person(String name){

 this.name=name;

 }

 public String toString ( ) {

 return name;

 }

}

and

public class Tester {

 static Person p=null;

 public static void main(String[] args) {

 p = checkperson(p);

 System.out.println(p);

 Person p1=new Person("Joe");

 p1=checkperson(p);

 System.out.println(p1);

 }

 public static Person checkperson(Person p) {

 if (p == null) {

 p = new Person("Mary");

 }

 return p;

 }

}

结果如何?

public class Tester{

 public static void main(String[] args) {

 float x=2,y=4,z=4;

 float a=y/x,b=y/z;

 if(a>b){

 System.out.println(a+b);

 }

 }

}

结果如何?

Locale l=new Locale("en","US");

LocalDate today=LocalDate.of(2018,12,17);

String mToday=

today.format(DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM));

String sToday= 

today.format(DateTimeFormatter.ofLocalizedDate(FormatStyle.SHORT));

System.out.println(mToday);

System.out.println(sToday);

结果如何?（答案有争议）

a code cleanup project for mlib.jar,you see this method invoked by customers:

public void enableService(String hostName,String portNumber)throws IOException{

this.transportSocket =new Socket(hostName,portNumber);

}

应该向该方法添加哪些安全措施，以满足客户可访问方法的需求?  （单选题 没有答案）

public class CreateArrayListExample{

 public static void main(String[] args) {

 List<String> vegetables=new ArrayList<>();

 vegetables.add("Kale");

 vegetables.add(0,"Lettuce");

 System.out.println(vegetables);

 List<char> fish=new ArrayList<>();

 fish.add("Salmon");

 fish.add(0,"Seabass");

 System.out.println(fish);

 }

}

结果如何?

public class Tester{

 private int x;

 private static int y;

 public static void main(String[] args) {

 Tester t1=new Tester();

 t1.x=2;

 Tester.y=3;

 Tester t2=new Tester();

 t2.x=4;

 t2.y=5;

 System.out.println(t1.x+","+t1.y);

 System.out.println(t2.x+","+Tester.y);

 System.out.println(t2.x+","+t1.y);

 }

}

结果如何?

Integer i=11;

which two statements compile?

interface MyInterface1{

 public int method() throws Exception;

 private void pMethod(){ }

}

interface MyInterface2{

 public static void sMethod(){ }

 public boolean equals();

}

interface MyInterface3{

 public void method();

 public void method(String str);

}

interface MyInterface4{

 public void dMethod(){ }

 public void method();

}

interface MyInterface5{

 public static void sMethod();

 public void method(String str);

}

哪两个接口可以在lambda表达式中使用?  

public interface ExampleInterface{

 static String origin="Interface";

 void exampleMethod(String first);

}

public abstract class ExampleAbstractClass{

 static String origin="Abstract Class";

 abstract void exampleMethod(String first,String second);

}

public class ExampleClass extends ExampleAbstractClass implements 

ExampleInterface{

 public void exampleMethod(String first) { }

 public void exampleMethod(String first, String second) {}

 public static void main(String[] args) {

 ExampleInterface theInterface=new ExampleClass();

//line n1

 }

}

哪两个单独插入到第n1行时会导致编译错误?  

 private String name;

 private String neighborhood;

 private int salary;

 //Constructors and setter and getter methods go here

}

and the code fragment:

List<Employee> roster=new ArrayList<>();

Predicate<Employee> p=e->e.getSalary()>30;

Function<Employee, Optional<String>> f=

e->Optional.ofNullable(e.getNeighborhood());

哪两个Map对象按社区将所有工资大于30的员工分组?