assert is a Java keyword used
to define an assert statement.
An assert statement is used to declare an expected boolean condition in a program.
If the program is running with assertions enabled, then the condition
is checked at runtime. If the condition is false, the Java runtime system
Assertions may be declared using the following syntax:
assert expression1 [: expression2];
expression1 is a boolean that will throw the assertion if it is false. When it is thrown, the assertion error exception is created with the parameter
expression2 (if applicable).
assert list != null && list.size() > 0 : "list variable is null or empty";
Object value = list.get(0);
Assertions are usually used as a debugging aid. They should not be used instead of validating arguments to public methods, or in place of a more precise runtime error exception.
Assertions are enabled with the Java
runtime option. See your Java environment documentation for additional options
for controlling assertions.