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Java - How to find Available Runtime Memory?

[Updated: Apr 8, 2020, Created: Apr 8, 2020]

Java 

Following example shows how to find available runtime memory in Java.

package com.logicbig.example;

import java.text.DecimalFormat;

public class MemoryUtil {
  //just to allocate some memory for demo
  static double[] arr = new double[1000000000];

  public static void main(String[] args) {
      String memoryInfo = getMemoryInfo();
      System.out.println(memoryInfo);
  }

  public static String getMemoryInfo() {
      long freeMemory = Runtime.getRuntime().freeMemory();
      long totalMemory = Runtime.getRuntime().totalMemory();
      return "Memory available: " + formatMemoryValue(freeMemory) + " / " + formatMemoryValue(totalMemory);
  }

  public static String formatMemoryValue(long size) {
      final String[] units = new String[]{"B", "KB", "MB", "GB", "TB"};
      int unitIndex = (int) (Math.log10(size) / Math.log10(1024));
      DecimalFormat decimalFormat = new DecimalFormat("#,##0.#");
      String formattedValue = decimalFormat.format(size / Math.pow(1024, unitIndex));
      return formattedValue + " " + units[unitIndex];
  }
}
Memory available: 257 MB / 640 MB

Let's specify -Xmx2g and -Xms2g

In Intellij:

Now run above class again:

Memory available: 1.6 GB / 2 GB

See Also