assert is a keyword added in Java version 1.4.
assert tests the programmer's assumption during development without writing exception handlers for an exception. Suppose you assumed that a number passed into a method will always be positive. While testing and debugging, you want to validate your assumption. Without the assert keyword, you will write a method like:
private void method(int a) {
if (a >= 0) {
// do something that depends on a not being negative
} else {
// tell the user that a is negative
}
}
This is simple exception handling; consider the case of big one. Assertion will come into the picture when you don't want to take the time to write the exception handling code.
Consider the above program with assertion:
private void method(int a) {
assert (a>=0); //throws an assertion error if a is negative.
// do stuff, knowing that a is not negative
}
In this program, assert (a>0) will pass when 'a' is only positive. Isn't this much cleaner than the previous example? If the value of 'a' is negative, then an AssertionError will be thrown.
There are two types of assertions:
Example of a really simple assertion:
private void method() {
assert (x>0);
//do more stuff
}
Example for simple assertion:
private void method() {
assert (x>0) : "X is" + x ;
// do more stuff
}
The difference between these two is that the simple assertion - the second example - appends the expression after the colon to the error description in the stack trace.
Note: assertion code - in effect - evaporates when the program is deployed.
For assertion first you need to invoke the assertion.
Asserts are disabled by default in the JVM. In order to run a program with asserts you must use the -ea command line parameter (i.e. java -ea AssertTest).
Even though your compiler suggested it was using java version 1.4, it wasn't actually because you compiled using the "javac [files]" command instead of the "javac -source 1.4 [files]" command. Assertions only work in version 1.4 and later versions.
When you are using assert keyword, you have to enable it. Otherwise it wont give any result.
java -enableassertions classfile
No, 'check' is not a keyword in java language.
assert (boolean expression); Example: assert (a >= 0);
No null is not a keyword. null is considered to be a "literal" in Java.
yes, float is keyword and data type in java
"verify" is not a Java keyword. I believe the link, in related links, has the complete list of Java keywords.
"int" is the keyword for integer
There is no "foreign" keyword in Java, however, there is a native keyword that declares native methods in a native language, such as C or C++.For full list of keywords in Java see related question.
string
Literal in java are L, F, null, true, false These act as keyword(have special meaning in java) but these does'nt comes under the category of Java Keyword.
"java" is the keyword/command used to execute Java Programs
In Java, the final keyword specifies that the object created cannot be further redefined or derived.
new is a keyword to create a instance of object any class.