1Z1-804 試験問題を無料オンラインアクセス

A valid reason to declare a class as abstract is to:

• A.prevent instance variables from being accessed
• B.define common method signatures in a class, while forcing child classes to contain unique method implementations
• C.define methods within a parent class, which may not be overridden in a child class
• D.define a class with methods that cannot be concurrently called by multiple threads
• E.prevent a class from being extended
• F.define a class that prevents variable state from being stored when object Instances are serialized

Given: What is the most likely result?

• A.a ConcurrentModification Exception is thrown
• B.size: 5, elements: 11 22 33 44 77
• C.size: 4, elements: 11 22 33 44
• D.size: 4, elements: 11 22 33 44 77
• E.size: 5, elements: 11 22 33 44

Given the code fragment: Which two try statements, when inserted at line ***, enable you to print files with the extensions.java, .htm, and .jar.

• A.try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir,"*. [java,htm,jar]")) {
• B.try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir,"*.{java*,htm*,jar*}")) {
• C.try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir,"**.{java,htm,jar}")) {
• D.try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir,"*.{java,htm,jar}")){

Which four are true about enums?

• A.An enum cannot have public methods or fields.
• B.An enum can implement an interface.
• C.An enum is typesafe.
• D.An enum can subclass another enum.
• E.All enums implicitly implement Comparable.
• F.An enum can declare a private constructor.

Given:
public class Main {
public static void main(String... ag) {
Vehicle v = new SportsCar();
System.out.println(v.goes());
Tank t = (Tank) v;
System.out.println(t);
}
}
class Vehicle {
public String goes() {
return "goes ";
};
}
class SportsCar extends Vehicle {
public String goes() {
return "fast ";
};
}
class Tank extends Vehicle {
public String goes() {
return "slow ";
}; }
What is the result?

• A.fast fast
• B.goes goes
• C.fast goes
• D.Compilation fails
• E.fast followed by an exception
• F.fast slow