Assertion

[meeta gaur]

class SimpleAssert    
{
	private void test(int i){
		assert(i>=0):"i="+i;
		System.out.println(i+" is not negative.");
	}
	public static void main(String[] args) 
	{
		SimpleAssert obj=new SimpleAssert();
		obj.test(-1);
	}
}

C:\>java -ea
Usage: java [-options] class [args...]
(to execute a class)
or java [-options] -jar jarfile [args...]
(to execute a jar file)
where options include:
-d32 use a 32-bit data model if available
-d64 use a 64-bit data model if available
-client to select the "client" VM
-server to select the "server" VM
-hotspot is a synonym for the "client" VM [deprecated]
The default VM is client.

-cp <class search path of directories and zip/jar files>
-classpath <class search path of directories and zip/jar files>
A ; separated list of directories, JAR archives,
and ZIP archives to search for class files.
-D<name>=<value>
set a system property
-verbose:[class|gc|jni]
enable verbose output
-version print product version and exit
-version:<value>
require the specified version to run
-showversion print product version and continue
-jre-restrict-search | -no-jre-restrict-search
include/exclude user private JREs in the version search
-? -help print this help message
-X print help on non-standard options
-ea[:<packagename>...|:<classname>]
-enableassertions[:<packagename>...|:<classname>]
enable assertions with specified granularity
-da[:<packagename>...|:<classname>]
-disableassertions[:<packagename>...|:<classname>]
disable assertions with specified granularity
-esa | -enablesystemassertions
enable system assertions
-dsa | -disablesystemassertions
disable system assertions
-agentlib:<libname>[=<options>]
load native agent library <libname>, e.g. -agentlib:hprof
see also, -agentlib:jdwp=help and -agentlib:hprof=help
-agentpath:<pathname>[=<options>]
load native agent library by full pathname
-javaagent:<jarpath>[=<options>]
load Java programming language agent, see java.lang.instrument
-splash:<imagepath>
show splash screen with specified image

C:\>java SimpleAssert
-1 is not negative.


After enabling assertion why it isn't enable when i ran program ?

If I'm wrong here then, could you please explain me meaning of first point in both snaps.

Thanks

[Matthew Brown]

Try java -ea SimpleAssert . The switch only enables assertions for the current execution. It doesn't mean that all following program runs will have assertions enabled.

The reason why you got all that usage printed out is that your first command, java -ea, doesn't actually do anything. It's telling you you need to provide a class to execute.

[meeta gaur]

Thanks i have tried that but please could you explain me meaning of first point in both snaps ?

i.e.

With no arguments (as in the preceding examples) Enables or disables assertions in all classes, except for the system classes.

[Matthew Brown]

They don't mean "no arguments to the java command". They're talking about arguments to the switches. Note from the examples that you can provide arguments to that using a colon. But they aren't examples of complete java calls, just the bits they're talking about.

So you can do this to run SimpleAssert with assertions turned on everywhere:

java -ea SimpleAssert

And you can do this to turn on assertions only in a particular package, while running SimpleAssert:

java -ea:mypackage... SimpleAssert