Simulate Java OutOfMemoryError

Simulate Java OutOfMemoryError

Here am simulating java OutOfMemoryError, lets discuss brief details about OutOfMemoryError.

Why OutOfMemoryError error will arise?

          OutOfMemoryError will arise when allotted Heap size of the Java virtual will be exceeds during runtime.

Where object will be saved in Java?

          Basically all java class objects will be saved during runtime in HeapMemory.

Sample Java Program to simulate OutOfMemoryError

In below program name is object of String, so name value will be saved to Heap space of JVM.

          Calling method1 infinite time will cause java.lang.OutOfMemoryError: Java heap space error, because below line in method1 is causing this error. If you comments below line you don’t get this error.

                         name+=";"+name;

package com.blogspot.microtechinfo;

public class JavaOutOfMemory {

            private static String  name="Marimuthu Rajagopal";

          private static int count=0;

         

          /**

           * @param args

           */

          public static void main(String[] args) {

                   // TODO Auto-generated method stub

                        while(true)

                   {

                             method1();

                   }

          }

          private static void method1()

          {

                  

                         name+=";"+name;

                   System.out.println("count="+ ++count);

                  

          }

         

}

 Output:

  

when count is 20 i will be getting  java.lang.OutOfMemoryError: Java heap space,It will vary based on machine.

count=1

count=2

count=3

count=4

count=5

count=6

count=7

count=8

count=9

count=10

count=11

count=12

count=13

count=14

count=15

count=16

count=17

count=18

count=19

count=20

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space

          at java.util.Arrays.copyOfRange(Unknown Source)

          at java.lang.String.(Unknown Source)

          at java.lang.StringBuilder.toString(Unknown Source)

          at com.blogspot.microtechinfo.JavaOutOfMemory.method1(JavaOutOfMemory.java:21)

          at com.blogspot.microtechinfo.JavaOutOfMemory.main(JavaOutOfMemory.java:15)

startsWith,endsWith Methods of String Class in Java

In this article, I am going to explains about endsWith,startsWith method in java String Class.

Let start explain about the two methods functionality.

startsWith(String arg)

                true, when the argument string is  matched with the “Prefix” of the another String, Otherwise false.

                Example :

                                String dbValue="s";

            boolean startValue="start".startsWith(dbValue);

            if(startValue)

            {

                  System.out.println("execute block of statement");

            }

            Here the value of variable startValue is “true”. So if statement will be executed and print as execute block of statement.

In real time variable dbvalue we used to get from the database/User interface. If we get the “empty” string value from the DB/UI than wired behavior will start.

I.e. we think that variable startValue is false and if statement won’t get executed, but variable  startValue will be  true and if statement get executed.

String dbValue="";

            boolean startValue="start".startsWith(dbValue);

            if(startValue)

            {

                  System.out.println("execute block of statement");

            }

Reason:

      The reason for return value true is comparison will be taken care by character sequence.so first character is consider as “empty character”.

endsWith(String arg)

true, when the argument string is  matched with the “Suffix” of the another String, Otherwise false.

            String dbValue="";

            boolean endValue="end".endsWith(dbValue);

if(endValue)

            {

                  System.out.println("execute block of statement");

            }

As same as the startsWith method variable  endValue will be  true and if statement get executed.