To set the JVM heap size, compile the program normally. For example, consider Runtime.java program. Compilation: javac Runtime.java Now, to set minimum heap size(let, 16 MB) required by JVM, run the program as follows : java -Xms16m Runtime We can also restrict maximum size(let 512 MB) utilized by JVM: java -Xmx512m Runtime Both these options can also be combined to specify upper and lower bounds of JVM heap size: java -Xms16m -Xmx512m Runtime Now you can run a program that requires huge computational space.