The java.lang.OutOfMemoryError: Java heap space error occurs when the Java Virtual Machine (JVM) does not have enough memory allocated to store objects and data in the heap.
Reasons for OutOfMemoryError: Java heap space:
1. Large object or data size:
If your program is dealing with large amounts of data or objects, it can quickly consume the available heap space.
2. Memory leaks:
If your program has memory leaks, it means that objects are not being properly garbage collected, leading to increased memory usage over time.
3. Insufficient heap size:
If the heap size is not large
enough to accommodate the memory requirements of your program, it can result in
an OutOfMemoryError.
Solutions for OutOfMemoryError: Java heap space:
1. Increase heap size:
You can allocate more memory to the JVM heap by setting the -Xmx flag. For example, java -Xmx2g MyClass sets the maximum heap size to 2 gigabytes.
2. Optimize memory usage:
Review your code and identify areas where memory usage can be optimized. Close resources properly, use efficient data structures, and avoid unnecessary object creation.
3. Stream and batch processing:
For large datasets, consider using stream processing or batch processing techniques to process data in smaller chunks instead of loading everything into memory at once.
4. Analyze and fix memory leaks:
Use profilers and memory analysis tools to identify and fix memory leaks in your code. Ensure that objects are properly released and no unnecessary references are retained.
Example:
import java.util.ArrayList;
import java.util.List;
public class OutOfMemoryExample {
public static void
main(String[] args) {
List<String> list = new ArrayList<>();
try {
while (true) {
String largeString
= new String(new char[1000000]);
list.add(largeString);
}
} catch (OutOfMemoryError
e) {
System.out.println("Out of memory
error occurred.");
}
}
}
In the above example, a large number of String objects
are created and added to the List. Eventually, the program will run out of heap
space and throw an OutOfMemoryError. To resolve this issue, you can either increase
the heap size using the -Xmx flag or optimize the code to reduce memory usage.
Reason:
Large object or data size
Example:
import java.util.ArrayList;
import java.util.List;
public class LargeDataExample {
public static void
main(String[] args) {
List<Integer>
largeList = new ArrayList<>();
for (int i = 0; i <
Integer.MAX_VALUE; i++) {
largeList.add(i);
}
}
}
Solution:
In STS, you can modify the heap size by adjusting the
VM arguments in the Run Configuration.
ü Right-click on your Java class file and select
"Run As" > "Run Configurations...".
ü Select your Java Application configuration.
ü Go to the "Arguments" tab.
ü In the "VM arguments" field, add -Xmx2g
to set the maximum heap size to 2GB.
Click "Apply" and "Run" to execute
the application with the increased heap size.
Reason:
Memory leaks - Not releasing objects properly
Example:
import java.util.ArrayList;
import java.util.List;
public class MemoryLeakExample {
private static List<Object> objectList = new ArrayList<>();
public static void
main(String[] args) {
while (true) {
Object object = new
Object();
objectList.add(object);
}
}
}
Solution:
ü Use profilers and memory analysis tools available in
STS to identify and fix memory leaks in your code.
ü Ensure that objects are properly released when they are no longer needed.
Reason:
Insufficient heap size
Example:
import java.util.ArrayList;
import java.util.List;
public class InsufficientHeapSizeExample {
public static void
main(String[] args) {
List<String> stringList = new
ArrayList<>();
while (true) {
String largeString =
"This is a large string that consumes a lot of memory";
stringList.add(largeString);
}
}
}
Remember to carefully analyze your specific
application and determine the best approach to address the OutOfMemoryError
based on the underlying cause. Based on above solution you can easily sove java errors.
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