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Increase heap size in Java

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How do I increase allocated heap size?

1)Change the gradle. properties file and change the heap size as per your requirement. 2)"Edit Custom VM Options" from the Help menu. It will open studio.

How much heap size we can increase?

You can increase to 2GB on a 32 bit system. If you're on a 64 bit system you can go higher.

What is heap size Java?

The default Java heap size is 1280 MB, which supports fewer than 75,000 pairs. If you increase the Java heap size by 256 MB, support increases by 25,000 pairs. You can continue to increase the Java heap size until you reach the maximum heap size.

How do I increase Java RAM usage?

The short answer is that you use these java command-line parameters to help control the RAM use of application: Use -Xmx to specify the maximum heap size. Use -Xms to specify the initial Java heap size. Use -Xss to set the Java thread stack size.


You can increase to 2GB on a 32 bit system. If you're on a 64 bit system you can go higher. No need to worry if you've chosen incorrectly, if you ask for 5g on a 32 bit system java will complain about an invalid value and quit.

As others have posted, use the cmd-line flags - e.g.

java -Xmx6g myprogram

You can get a full list (or a nearly full list, anyway) by typing java -X.


It is possible to increase heap size allocated by the JVM by using command line options Here we have 3 options

-Xms<size>        set initial Java heap size
-Xmx<size>        set maximum Java heap size
-Xss<size>        set java thread stack size

java -Xms16m -Xmx64m ClassName

In the above line we can set minimum heap to 16mb and maximum heap 64mb


On a 32-bit JVM, the largest heap size you can theoretically set is 4gb. To use a larger heap size, you need to use a 64-bit JVM. Try the following:

java -Xmx6144M -d64

The -d64 flag is important as this tells the JVM to run in 64-bit mode.


You can increase the Heap Size by passing JVM parameters -Xms and -Xmx like below:

For Jar Files:

java -jar -Xms4096M -Xmx6144M jarFilePath.jar

For Java Files:

 java -Xms4096M -Xmx6144M ClassName

The above parameters increase the InitialHeapSize (-Xms) to 4GB (4096 MB) and MaxHeapSize(-Xmx) to 6GB (6144 MB).

But, the Young Generation Heap Size will remain same and the additional HeapSize will be added to the Old Generation Heap Size. To equalize the size of Young Gen Heap and Old Gen Heap, use -XX:NewRatio=1 -XX:-UseAdaptiveSizePolicy params.

java -jar -Xms4096M -Xmx6144M -XX:NewRatio=1 -XX:-UseAdaptiveSizePolicy pathToJarFile.jar

-XX:NewRatio = Old Gen Heap Size : Young Gen HeapSize (You can play with this ratio to get your desired ratio).


It is possible to increase heap size allocated by the JVM in eclipse directly In eclipse IDE goto

Run---->Run Configurations---->Arguments

Enter -Xmx1g(It is used to set the max size like Xmx256m or Xmx1g...... m-->mb g--->gb)