1Z0-829: Java SE 17 DeveloperDemo

"Java" begins at zero-based index 7 in "Hello! Java". Because String objects are immutable, the unassigned result of a.replace("Hello!", "Welcome!") does not change a. The StringBuilder is therefore constructed from the unchanged value, and all three indexOf("Java") calls return 7, producing 777.

Java passes the int argument by value, so incrementing the method parameter changes it from 1000 to 1001 only within myMethod. The expression this.x refers to the instance field, which remains 100. The local variable in main also remains 1000, producing 10011001000.

A top-down Java module migration begins with the application or higher-level dependent module and proceeds through its required dependencies. Required dependencies must be available on the module path—initially, they can be automatic modules—because a named module cannot read the unnamed module.

~2 evaluates to -3, and 2 ^ -3 evaluates to -1. The & operator evaluates both boolean operands, so the first c++ executes and changes c to 0 even though the left comparison is false. The && expression then evaluates its right operand because its left operand is true, incrementing c to 1. The output is false 0true 1.

Overload resolution chooses the applicable method with the most specific valid conversion. sum(10, 15.25) and sum(10.25, 10.25) cannot use the fixed-arity float overloads because converting a double to float is narrowing; both invoke sum(double... a). sum(10, 24) exactly matches sum(int, int). Therefore, the output is D A D.

The identity value in the three-argument parallel reduction is applied to each partial reduction. The two elements produce the partial strings wTable and wChair, and the combiner concatenates them to wTablewChair. The identity-free reduction concatenates Table and Chair, yielding TableChair.

Because Software implements Serializable, its Game subclass is serializable as well. Serialization saves the title and players fields, while deserialization does not run constructors of serializable classes. The initial construction prints Software Game , and the deserialized object's overridden toString() returns Chess 2, producing Software Game Chess 2.

LuxuryCar is already serializable because every subtype of a serializable class is serializable. Deserializing it and casting it to Car is valid. The stream operations can throw IOException, while readObject() can throw both IOException and ClassNotFoundException; therefore, the main method must declare those two checked exceptions for the code to compile and print the value.

Reader.read(char[]) returns the number of characters read and stores only those characters in the supplied array. Writer.write(char[]) writes the entire character array. After the first 8-character read, the buffer is 01234567. The final 2-character read replaces only its first two positions with 89, leaving 234567 in the remaining positions; writing the whole buffer therefore appends 89234567.

A text block whose closing delimiter appears immediately after its final content character has no final line terminator, so myTextBlk1 equals "Hello Java 17". When the closing delimiter is on its own following line, the text block includes a final line-feed, making myTextBlk2 a different string. String.intern() returns canonical representations of equal string values, but these two values are not equal. Oracle: Text Blocks

A try-with-resources resource must implement AutoCloseable, and its close() method is invoked automatically when the block exits. Implementing AutoCloseable and providing the public close() method that prints Close satisfy those requirements; declaring IOException is permitted because AutoCloseable.close() may throw Exception.

The object referenced by cobj is an instance of C, which is also an instance of B. Therefore v.mB() executes, followed by v1.mC() after the nested instanceof C test succeeds. The output is mBmC.

tryLock() makes an immediate attempt to acquire the lock and returns a boolean result whether acquisition succeeds or fails; it does not wait for the lock. In contrast, lock() waits until it obtains the lock and has no boolean return value.

10_00 is a valid integer literal whose value is 1000, so adding 250 + s2 produces 1250. Java permits underscores within numeric literals, but Integer.parseInt and Integer.valueOf do not accept underscores in a string representation. No second listed statement independently prints 1250; the item’s instruction to choose two is inconsistent with its options.

A static method cannot directly access an instance field. Declaring name as static makes it a class field, so it can be accessed from the static display() method. The non-static overload still compiles, even though accessing a static field through this is discouraged.

valueOf("CMO") resolves to the enum constant CMO because enum lookup requires the exact declared constant name. The switch therefore selects case CMO and prints Marketing. The unused stream pipeline does not print anything. Java Enum API

A default interface method is a public instance method with an implementation, so MyC inherits m2 and it can be called on a MyC object. A static interface method is invoked using its declaring interface name, so IFace.m3() is valid. Private interface methods are accessible only within their declaring interface, and static interface methods are not inherited by implementing classes or available through an instance reference. Java Language Specification, Chapter 9: Interfaces

Files.lines produces a stream of the file’s lines, so joining the three lines with "-" prints text1-text2-text3. Files.readAllLines returns a list with three elements, whose valid indexes are 0, 1, and 2; requesting index 3 throws IndexOutOfBoundsException. Because only IOException is caught, that runtime exception is not handled.

permits WordDoc denotes p1.WordDoc. A direct subclass of a sealed class must explicitly be declared final, sealed, or non-sealed. Therefore, the final declaration and both non-sealed declarations in package p1 are valid. An abstract class may also be non-sealed; the Java Language Specification does not require such a permitted subclass to be public. The item consequently contains three valid choices, despite instructing the reader to choose two.

Object.wait() and Thread.join() are interruptible waiting operations that declare the checked InterruptedException; invoking code must catch it or declare it. A waiting thread does not consume CPU time, and expiration of a timed wait permits execution to resume rather than terminating the thread. Oracle Java Thread API

A transient instance field is not saved during serialization, so price is restored with its default float value of 0.0. The custom readObject(ObjectInputStream) hook must be declared private to be used by Java serialization; the public method is ignored. The static averagePrice field remains 2.99, so the output is Cookie 0.0 2.99.

Enum ordinals are zero-based, so SUNNY.ordinal() is 0. valueOf("CLOUDY") returns the CLOUDY enum constant, and printing it calls the enum's overridden toString() method, which returns "SNOWY".

Truncating an Instant to ChronoUnit.MINUTES rounds it down to the minute by setting seconds and nanoseconds to zero. Both timestamps therefore become 2021-01-12T21:58:00Z; neither is after the other, so the else branch prints Can't logout.