Career: Java Reserved Words

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abastract

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An abstract class is a class that is declared abstract—it may or may not include abstract methods. Abstract classes cannot be instantiated, but they can be subclassed.
An abstract method is a method that is declared without an implementation

Unlike interfaces, abstract classes can contain fields that are not static and final, and they can contain implemented methods. Such abstract classes are similar to interfaces, except that they provide a partial implementation, leaving it to subclasses to complete the implementation. If an abstract class contains only abstract method declarations, it should be declared as an interface instead.

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assert

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An assertion is a statement in the Java programming language that enables you to test your assumptions about your program.

The assertion statement has two forms. The first, simpler form is:

assert Expression1 ;
where Expression1 is a boolean expression. When the system runs the assertion, it evaluates Expression1 and if it is false throws an AssertionError with no detail message.
The second form of the assertion statement is:

assert Expression1 : Expression2 ;
where:

Expression1 is a boolean expression.
Expression2 is an expression that has a value. (It cannot be an invocation of a method that is declared void.)
Use this version of the assert statement to provide a detail message for the AssertionError. The system passes the value of Expression2 to the appropriate AssertionError constructor, which uses the string representation of the value as the error's detail message.

Do not use assertions to do any work that your application requires for correct operation.
Because assertions may be disabled, programs must not assume that the boolean expression contained in an assertion will be evaluated.

Do not use assertions for argument checking in public methods.
Argument checking is typically part of the published specifications (or contract) of a method, and these specifications must be obeyed whether assertions are enabled or disabled. Another problem with using assertions for argument checking is that erroneous arguments should result in an appropriate runtime exception (such as IllegalArgumentException, IndexOutOfBoundsException, or NullPointerException). An assertion failure will not throw an appropriate exception.

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boolean

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The boolean primative data type has only two possible values: true and false. Use this data type for simple flags that track true/false conditions. This data type represents one bit of information, but its "size" isn't something that's precisely defined.

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break

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The break statement has two forms: labeled and unlabeled. You saw the unlabeled form in the previous discussion of the switch statement. You can also use an unlabeled break to terminate a for, while, or do-while loop.

The labeled break statement terminates the labeled statement; it does not transfer the flow of control to the label. Control flow is transferred to the statement immediately following the labeled (terminated) statement.

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byte

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The byte data type is an 8-bit signed two's complement integer. It has a minimum value of -128 and a maximum value of 127 (inclusive). The byte data type can be useful for saving memory in large arrays, where the memory savings actually matters. They can also be used in place of int where their limits help to clarify your code; the fact that a variable's range is limited can serve as a form of documentation.

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case

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The body of a switch statement is known as a switch block. Any statement immediately contained by the switch block may be labeled with one or more case or default labels. The switch statement evaluates its expression and executes the appropriate case.

i.e. case 1: System.out.println("January"); break;

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catch

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The catch block contains code that is executed if and when the exception handler is invoked. The runtime system invokes the exception handler when the handler is the first one in the call stack whose ExceptionType matches the type of the exception thrown. The system considers it a match if the thrown object can legally be assigned to the exception handler's argument.

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char

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char: The char data type is a single 16-bit Unicode character. It has a minimum value of '\u0000' (or 0) and a maximum value of '\uffff' (or 65,535 inclusive).

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class

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A class is the blueprint from which individual objects are created.

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const

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(not used)

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continue

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The continue statement skips the current iteration of a for, while , or do-while loop. The unlabeled form skips to the end of the innermost loop's body and evaluates the boolean expression that controls the loop.

A labeled continue statement skips the current iteration of an outer loop marked with the given label

test:
for (int i = 0; i <= max; i++) {
int n = substring.length();
int j = i;
int k = 0;
while (n-- != 0) {
if (searchMe.charAt(j++)
!= substring.charAt(k++)) {
continue test;
}
}
foundIt = true;
break test;
}

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default

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The default section handles all values that aren't explicitly handled by one of the case sections. (in a switch statement)

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do

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The difference between do-while and while is that do-while evaluates its expression at the bottom of the loop instead of the top. Therefore, the statements within the do block are always executed at least once,

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double

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double: The double data type is a double-precision 64-bit IEEE 754 floating point. Its range of values is beyond the scope of this discussion, but is specified in section 4.2.3 of the Java Language Specification. For decimal values, this data type is generally the default choice. As mentioned above, this data type should never be used for precise values, such as currency.

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else

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The if-then-else statement provides a secondary path of execution when an "if" clause evaluates to false

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enum

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An enum type is a type whose fields consist of a fixed set of constants.

All enums implicitly extend java.lang.Enum. Since Java does not support multiple inheritance, an enum cannot extend anything else.

Java programming language enum types are much more powerful than their counterparts in other languages. The enum declaration defines a class (called an enum type). The enum class body can include methods and other fields.

public enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
THURSDAY, FRIDAY, SATURDAY
}

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extends

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A subclass inherits all of the public and protected members of its parent, no matter what package the subclass is in. If the subclass is in the same package as its parent, it also inherits the package-private members of the parent. You can use the inherited members as is, replace them, hide them, or supplement them with new members:

* The inherited fields can be used directly, just like any other fields.
* You can declare a field in the subclass with the same name as the one in the superclass, thus hiding it (not recommended).
* You can declare new fields in the subclass that are not in the superclass.
* The inherited methods can be used directly as they are.
* You can write a new instance method in the subclass that has the same signature as the one in the superclass, thus overriding it.
* You can write a new static method in the subclass that has the same signature as the one in the superclass, thus hiding it.
* You can declare new methods in the subclass that are not in the superclass.
* You can write a subclass constructor that invokes the constructor of the superclass, either implicitly or by using the keyword super.