Skip to content
Related Articles

Related Articles

Improve Article
Save Article
Like Article

Java Program to Set Minimum and Maximum Heap Size

  • Difficulty Level : Basic
  • Last Updated : 09 Jun, 2021

The Heap area is one of the various memory areas present inside the JVM.  For every JVM one heap area is available. The Heap area will be created at the time of the JVM startup. Objects and the corresponding instance variable will be stored in the heap area. Every array in java is the object only, hence the array also will be stored in the heap area. The Heap area can be accessed by multi threads hence the data store in heap memory is not threaded safe. The Heap area need not be continuous.

Program to display heap memory statistics:

Attention reader! Don’t stop learning now. Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready. To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

A java application can communicate with VM by using a runtime object. Runtime class present in java.lang package and it is a singleton class. We can create a runtime object as follows:

Runtime r= Runtime.getRuntime();



Once we get the runtime object we can call the following methods on that object :

  • maxMemory() : It returns the number of bytes of max memory allocated to the heap.
  • totalMemory() : It returns the number of bytes of the total memory allocated to the heap.
  • freeMemory() : It returns the number of bytes of free memory present in the heap

Java




// import required packages
import java.io.*;
import java.lang.*;
import java.util.*;
 
// driver class
class heapMemory {
 
    // main method
    public static void main(String[] args)
    {
        // creating runtime time object
        Runtime r = Runtime.getRuntime();
 
        // displaying max memory of heap in bytes
        System.out.println("Max memory"
                           + " " + r.maxMemory());
 
        // displaying initial memory in bytes
        System.out.println("Initial memory"
                           + " " + r.totalMemory());
 
        // displaying free memory in bytes
        System.out.println("Free memory"
                           + " " + r.freeMemory());
 
        // displaying consume memory in bytes
        System.out.println(
            "Consume memory"
            + " " + (r.totalMemory() - r.freeMemory()));
    }
}
Output
Max memory 134217728
Initial memory 134217728
Free memory 132286176
Consume memory 1931552

Heap memory is finite memory but based on our requirements we can set maximum and minimum heap size i.e we can increase or decrease the heap size based on our requirements. We can do this by using the following java commands at runtime.

1. -Xmx to set maximum heap size (max memory)

                java -Xmx512m heapMemory

This command sets the maximum heap size as 512Mb.

Java




// import required packages
import java.io.*;
import java.lang.*;
import java.util.*;
 
// driver class
class heapMemory {
 
    // main method
    public static void main(String[] args)
    {
        double mb = 1000000;
 
        // creating runtime time object
        Runtime r = Runtime.getRuntime();
 
        // displaying max memory of heap in Mb
        System.out.println("Max memory"
                           + " " + r.maxMemory() / mb);
 
        // displaying initial memory in Mb
        System.out.println("Initial memory"
                           + " " + r.totalMemory() / mb);
 
        // displaying free memory in Mb
        System.out.println("Free memory"
                           + " " + r.freeMemory() / mb);
 
        // displaying consume memory in Mb
        System.out.println(
            "Consume memory"
            + " "
            + (r.totalMemory() - r.freeMemory()) / mb);
    }
}
Output
Max memory 134.217728
Initial memory 134.217728
Free memory 132.285184
Consume memory 1.932544

2. -Xms: we can use this command to set a minimum or initial heap size.

 java  -Xms64m heapMemory

This command set the minimum size as 64Mb i.e totalMemory().

Java




// import required packages
import java.io.*;
import java.lang.*;
import java.util.*;
 
// driver class
class heapMemory {
 
    // main method
    public static void main(String[] args)
    {
        double mb = 1000000;
 
        // creating runtime time object
        Runtime r = Runtime.getRuntime();
 
        // displaying max memory of heap in Mb
        System.out.println("Max memory"
                           + " " + r.maxMemory() / mb);
 
        // displaying initial memory in Mb
        System.out.println("Initial memory"
                           + " " + r.totalMemory() / mb);
 
        // displaying free memory in Mb
        System.out.println("Free memory"
                           + " " + r.freeMemory() / mb);
 
        // displaying consume memory in Mb
        System.out.println(
            "Consume memory"
            + " "
            + (r.totalMemory() - r.freeMemory()) / mb);
    }
}
Output
Max memory 134.217728
Initial memory 134.217728
Free memory 132.285192
Consume memory 1.932536

 




My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!