Netbean : java.lang.OutOfMemoryError: Java heap space - Solutions

In java application development, sometimes your application will throw an exception

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at com.classpackage.MainConsole.main(
Java Result: 1

This is because your program consuming a lot of memory. One of the solutions is to increase the Xms and Xmx argument on the project.

Lets see the example :

The Main Class

import java.util.ArrayList;
import java.util.List;

public class MainConsole {
    public static void main(String[] args){
        List<PhoneContacts> phoneContacts = new ArrayList<PhoneContacts>();
        // You can use diamond inference in JDK 7 like example below
        //List<PhoneContacts> phoneContacts = new ArrayList<>();
        for(int index = 0;index< 10000000;index++ ){
            PhoneContacts p = new PhoneContacts();
            p.setFirstName("developersnote" + Integer.toString(index));
            p.setLastName("developersnote" + Integer.toString(index));
        for(PhoneContacts p : phoneContacts){

The Phone Contacts Class

public class PhoneContacts {
    private String firstName;
    private String lastName;
    private String phoneNumber;

    public String getFirstName() {
        return firstName;

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    public String getLastName() {
        return lastName;
    public void setLastName(String lastName) {
        this.lastName = lastName;
    public String getPhoneNumber() {
        return phoneNumber;
    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;

The above example will cause out of memory exception . So the solutions is to increase the argument in JVM. Lets see the solution below.

The Solutions

  1. Right click  on the java project >> properties
  2. Set the VM options -Xms512m -Xmx1024m  (You can increase the value -Xmx to the suitable maximum memory allocation depends on your project memory consumption).  
  3. Refer this post -X Command line options post for more information

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