12 Δεκ Which of the following Statements Are Legal Declarations and Definitions of a Method
You cannot declare multiple methods with the same name and the same number and type of arguments because the compiler cannot distinguish them. Retrieving the lock associated with an object does not prevent other threads from accessing the object`s fields or calling methods that are not synchronized on the object. Other threads may also use synchronized methods or the traditionally synchronized statement to achieve mutual exclusion. In the Graph class of §14.15, one of the break statements is used to complete the execution of the entire body of the outermost for loop. This interruption can be replaced by a continuation if the for loop itself is labeled: before discussing legal and illegal instructions, let`s look at how variables are declared and initialized in C. Methods are distinguished by the compiler by the number and type of arguments passed to the method. Therefore, draw(String s) and draw(int i) are different and unique methods. You cannot declare multiple methods with the same signature: draw(String s) and draw(String t) are identical and result in a compiler error. Note that overloaded methods must return the same data type. Therefore, void draw(String s) and int draw(String t) declared in the same class produce a compile error. The Java programming language, like C and C++ and many programming languages before them, arbitrarily dictates that an else clause belongs to the intimate to which it might belong. This rule is captured by the following grammar: The data type of the value returned by the return statement must match the type of data that the method should return.
You cannot return an object from a declared method to return an integer. When returning an object, the data type of the returned object must be a subclass of or exactly the specified class. When returning an interface type, the returned object must implement the specified interface. Responses that say “definition” refers to the point at which the variable is initialized are explicitly not supported by the Java specification. In Java, a variable is initialized at the declaration point or in a later map. In the latter case, no specific term is used. or requires. outside of assignment and/or initialization. There is no set point to which memory is allocated for the variable. In fact, it is possible that the space for the variable itself is allocated before the declaration is reached. A continuous instruction can only occur in a certain time, do or for instruction.
Statements of these three types are called iteration statements. Control is passed to the loop continuation point of an iteration statement. As in C and C++, the execution of instructions in a switch block is done “through labels”. However, it is not legal to use an expression in parentheses (§15.8.5): The following program combines the extended for statement with automatic unpacking to translate a histogram into a frequency table: There are many types of statements in the Java programming language. Most correspond to instructions in C and C++, but some are unique. Declaration: A statement that creates an identifier and maps attributes to it without necessarily reserving its memory (for data) or providing the implementation (for methods). Methods can return primitive data type values or reference data types. The isEmpty() method of the Stack class returns a primitive data type, a Boolean value: Method declared with void keyword to return no value (§8.4.5) The first statement of the foo method creates an instance of the Global.Cyclic member class instead of an instance of the Cyclic local class, because the statement appears before the scope of the local class declaration. With this in mind, assertions should not be used to validate arguments in public methods. Validating arguments is usually part of a method`s contract, and it must be respected regardless of whether the assertions are enabled or disabled.
The following is an example of a typical method declaration: is given by the following translation as a basic try-with-resources statement nested within a try-catch or try-finally or try-catch-finally statement: A secondary issue with using assertions for argument validation is that incorrect arguments must result in an appropriate run-time exception (for example, IllegalArgumentException, ArrayIndexOutOfBoundsException, or NullPointerException). An assertion error does not throw a corresponding exception. Again, it is not illegal to use allegations to verify public methods, but it is generally inappropriate. It is expected that AssertionError will never be detected, but it is possible to do so, so the rules of try statements should treat assertions that appear in a try block in the same way as the current handling of thrun statements. Because assertions can be disabled, programs should not assume that expressions in assertions are evaluated. Therefore, these Boolean expressions should generally be free of side effects. The evaluation of such a Boolean expression should not affect a visible state after the evaluation is complete. It is not illegal for a Boolean expression contained in an assertion to have a side effect, but it is generally inappropriate because it can vary the behavior of the program depending on whether the assertions have been enabled or disabled. In the following example, a mathematical graph is represented by an array of arrays. A graph consists of a set of vertices and a set of edges; Each edge is an arrow pointing from one node to another node or from one node to itself. This example assumes that there are no redundant edges.
That is, for any two nodes P and Q, where Q can be identical to P, there is at most one edge from P to Q. The if statement allows conditional execution of a statement or conditional selection of two statements, one or the other, but not both. The above descriptions say “transfer control attempts” and not just “transfer control”, because if there are try statements (§ 14.20) in the break target whose try blocks or catch clauses contain the break statement, then all clauses of those try statements are executed, in order, from the innermost to the outermost, before the control is transferred to the break target. Abruptly closing a finally clause can disrupt the control transition initiated by a break statement. For example, suppose you have a class that can use calligraphy to draw different types of data (strings, integers, and so on) and that contains a method to draw each type of data. It is tedious to use a new name for each method, such as drawString, drawInteger, drawFloat, etc. In the Java language, you can use the same name for all drawing methods, but pass a different list of arguments for each method. Therefore, the data drawing class can declare four methods named draw, each with a different list of parameters. Classes: Java does not really separate declarations and definitions like C++ (in header and cpp files). You define them where you declare them. If no case label matches, but there is a default label, all statements after the default label in the switch block, if any, are executed sequentially.
An abrupt conclusion is always associated with a reason, which is one of the following: The case of an abrupt conclusion due to a break with a label is dealt with by the general rule for labelled declarations (§ 14.7). An unlabeled break statement attempts to pass control to the innermost encompassing switch, while, do, or for instruction of the immediate encapsulation method or initializer. This statement, called the pause target, completes immediately normally. If an exception parameter is indeed final (in a uni-catch clause) or implicitly final (in a multicatch clause), adding an explicit final modifier to its declaration does not cause errors at compile time. However, if the exception parameter of a uni-catch clause is explicitly declared final, removing the finally modifier can cause errors at compile time because the exception parameter, which is now considered final effective, can no longer be referenced by anonymous and local class declarations in the body of the catch clause. If there are no compilation errors, it is possible to modify the program further so that the exception parameter in the body of the catch clause is reassigned and is therefore no longer considered final effective. Each statement has a normal execution mode in which certain calculation steps are performed. The following sections describe the normal execution mode for each type of statement.
A block is executed by executing each of the local variable declaration statements and other statements in order from first to last (left to right). If all these block statements complete normally, the block completes normally.