Oracle 1z0-830 Exam With Confidence Using Practice Dumps

In this code, the Calculable interface defines a single abstract method calculate that takes an int parameter and returns a long. The main method contains three lambda expressions assigned to variables c1, c2, and c3 of type Calculable.

Line 1:Calculable c1 = i -> i + 1;

This lambda expression takes an integer i and returns the result of i + 1. Since the expression i + 1 results in an int, and Java allows implicit widening conversion from int to long, this line compiles successfully.

Line 2:Calculable c2 = i -> Long.valueOf(i);

Here, the lambda expression takes an integer i and returns the result of Long.valueOf(i). The Long.valueOf(int i) method returns a Long object. However, Java allows unboxing of the Long object to a long primitive type when necessary. Therefore, this line compiles successfully.

Line 3:Calculable c3 = i -> { throw new ArithmeticException(); };

This lambda expression takes an integer i and throws an ArithmeticException. Since the method calculate has a return type of long, and throwing an exception is a valid way to exit the method without returning a value, this line compiles successfully.

Since all three lines adhere to the method signature defined in the Calculable interface and there are no type mismatches or syntax errors, the program compiles successfully.

In Java generics, wildcards are used to relax the type constraints of generic types. The extends wildcard () denotes an upper bounded wildcard, allowing any type that is a subclass of Type. Conversely, the super wildcard () denotes a lower bounded wildcard, allowing any type that is a superclass of Type.

Option A:

java

public List getListSuper() {

return new ArrayList();

}

Here, List represents a list that can hold IOException objects and objects of its supertypes. Since Exception is a superclass of IOException, ArrayList is compatible with List. Therefore, this method compiles successfully.

Option B:

java

public List getListExtends() {

return new ArrayList();

}

In this case, List represents a list that can hold objects of IOException and its subclasses. Since FileNotFoundException is a subclass of IOException, ArrayList is compatible with List. Thus, this method compiles successfully.

Option C:

java

public List getListExtends() {

return new ArrayList();

}

Here, List expects a list of IOException or its subclasses. However, Exception is a superclass of IOException, not a subclass. Therefore, ArrayList is not compatible with List, and this method will not compile.

Option D:

java

public List getListSuper() {

return new ArrayList();

}

In this scenario, List expects a list that can hold IOException objects and objects of its supertypes. Since FileNotFoundException is a subclass of IOException, ArrayList is not compatible with List, and this method will not compile.

Therefore, the methods in options A and B compile successfully, while those in options C and D do not.

1. Understanding Supplier Functional Interfaces

The Supplier interface is part of java.util.function and provides valueswithout taking any arguments.

Java also provides primitive specializations of Supplier:

BooleanSupplier→ Returns a boolean. Exists

DoubleSupplier→ Returns a double. Exists

LongSupplier→ Returns a long. Exists

Supplier<T>→ Returns a generic T. Exists

2. What about BiSupplier<T, U, R>?

There is no BiSupplier<T, U, R> in Java.

In Java, suppliers donot take arguments, so abi-supplierdoes not exist.

If you need a function thattakes two arguments and returns a value, use BiFunction.

Thus, the correct answer is:BiSupplier<T, U, R> does not exist.

References:

Java SE 21 - Supplier

Java SE 21 - Functional Interfaces