JVM "-ea" and "-da" Options

This section describes '-ea' and '-da' JVM option, which are used to enable or disable assertion on application classes.

By default, "assert" statements in your are not execution to save execution time. If you are running a Java application with "assert" statements added, you can turn on the JVM assertion option to troubleshoot execution issues.

JVM ("java" command) supports a number of assertion options:

Let's re-run the sample program in the previous tutorial with the "-ea" option:

herong> java -ea AssertStatementTest.java 8
Hour specified: 8
Good morning!

herong> java -ea AssertStatementTest.java 18
Hour specified: 18
Good evening!

herong> java -ea AssertStatementTest.java 28
Hour specified: 28
Exception in thread "main" java.lang.AssertionError:
  Hour = 28. It be must be < 24.
	at AssertStatementTest.greeting(AssertStatementTest.java:19)
	at AssertStatementTest.main(AssertStatementTest.java:10)

herong> java -ea AssertStatementTest.java -8
Hour specified: -8
Exception in thread "main" java.lang.AssertionError:
  Hour = -8. It be must be >= 0.
	at AssertStatementTest.greeting(AssertStatementTest.java:16)
	at AssertStatementTest.main(AssertStatementTest.java:10)

As you can see, both "assert" statements were exected. AssertionError messages were corrected generated.

Table of Contents

 About This Book

 JDK - Java Development Kit

 Execution Process, Entry Point, Input and Output

 Primitive Data Types and Literals

 Control Flow Statements

 Bits, Bytes, Bitwise and Shift Operations

 Managing Bit Strings in Byte Arrays

 Reference Data Types and Variables

 Enum Types and Enum Constants

 StringBuffer - The String Buffer Class

 System Properties and Runtime Object Methods

 Generic Classes and Parameterized Types

 Generic Methods and Type Inference

 Lambda Expressions and Method References

 Java Modules - Java Package Aggregation

 Execution Threads and Multi-Threading Java Programs

 ThreadGroup Class and "system" ThreadGroup Tree

 Synchronization Technique and Synchronized Code Blocks

 Deadlock Condition Example Programs

 Garbage Collection and the gc() Method

Assert Statements and -ea" Option

 "assert" Statements

JVM "-ea" and "-da" Options

 Annotation Statements and Declarations

 Java Related Terminologies

 Outdated Tutorials

 References

 Full Version in PDF/EPUB