A Simple Test Class to Test the Assert Statement - Java Language Basics

Java examples for Language Basics:assert

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Description

A Simple Test Class to Test the Assert Statement

Demo Code

public class Main {
  public static void main(String[] args) {
    int x = 10 + 15;
    assert x == 100:"x = " + x; // should throw an AssertionError
  }/*from  w w w.j  a v  a2 s .c o m*/
}

Testing Assertions

Try to run the Main class using the following command: 

java -ea Main

Command-Line Switches to Enable/Disable Assertions at Runtime

Command-Line Switch Description
-enableassertions or -ea Used to enable assertions at runtime for system classes as well as user-defined classes. You can pass an argument to this switch to control the level at which assertions are enabled.
-disableassertions or -da Used to disable assertions at runtime for system classes as well as user-defined classes. You can pass an argument to this switch to control the level at which assertions are disabled.
-enablesystemassertions or -esa Used to enable assertions in all system classes. You cannot pass any arguments to this switch.
-disablesystemassertions or -dsa Used to disable assertions in all system classes. You cannot pass any arguments to this switch. 
 
/* Enable assertions in all system classes */ 
java -esa Main
  
/* Enable assertions in all user-defined classes */ 
java -ea Main
  
/* Enable assertions in com.mypkg package and its sub-packages */ 
java -ea:com.mypkg... com.mypkg.assertion.AssertTest 
  
/* Enable assertions in the unnamed package in the current directory */ 
java -ea:... com.mypkg.assertion.AssertTest 
  
/* Enable assertions in com.mypkg.assertion.AssertTest class */ 
java -ea:com.mypkg.assertion.AssertTest com.mypkg.assertion.AssertTest 
  
 
/* Enable assertions in p1 package and all its sub-packages and disable assertion for p1.p2.MyClass  */ 
java -ea:p1... -da:p1.p2.MyClass com.mypkg.assertion.AssertTest

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