“Error occurred during initialization of VM; Could not reserve enough space for object heap” using -Xmx3G
Could it be that you’re using a 32-bit jvm on that machine?
java
What is the “continue” keyword and how does it work in Java?
A continue statement without a label will re-execute from the condition the innermost while or do loop, and from the update expression of the innermost for loop. It is often used to early-terminate a loop’s processing and thereby avoid deeply-nested if statements. In the following example continue will get the next line, without processing the following statement in the loop. With a label, continue will re-execute from the loop … Read more
What does value & 0xff do in Java?
It sets result to the (unsigned) value resulting from putting the 8 bits of value in the lowest 8 bits of result. The reason something like this is necessary is that byte is a signed type in Java. If you just wrote: then result would end up with the value ff ff ff fe instead of 00 00 00 fe. A further subtlety is that the & is defined … Read more
What is a JavaBean exactly?
A JavaBean is just a standard All properties are private (use getters/setters) A public no-argument constructor Implements Serializable. That’s it. It’s just a convention. Lots of libraries depend on it though. With respect to Serializable, from the API documentation: Serializability of a class is enabled by the class implementing the java.io.Serializable interface. Classes that do not implement this interface will not … Read more
Converting double to string
This will convert double to String
What is float in Java?
In Java, when you type a decimal number as 3.6, its interpreted as a double. double is a 64-bit precision IEEE 754 floating point, while floatis a 32-bit precision IEEE 754 floating point. As a float is less precise than a double, the conversion cannot be performed implicitly. If you want to create a float, you should end your number with f (i.e.: 3.6f).
Could not reserve enough space for object heap
Run the JVM with -XX:MaxHeapSize=512m (or any big number as you need) (or -Xmx512m for short)
Integer division in Java [duplicate]
They are being divided in integer arithmetics. So dividing integer a by integer b you get how many times b fits into a. Also a % b will give you a remainder of a division. So (a / b ) * b + a % b = a
Is Java “pass-by-reference” or “pass-by-value”?
Java is always pass-by-value. Unfortunately, when we deal with objects we are really dealing with object-handles called references which are passed-by-value as well. This terminology and semantics easily confuse many beginners. It goes like this: In the example above aDog.getName() will still return “Max”. The value aDog within main is not changed in the function foo with the Dog “Fifi” as the object reference is passed by value. If it … Read more
How can I solve “java.lang.NoClassDefFoundError”?
After you compile your code, you end up with .class files for each class in your program. These binary files are the bytecode that Java interprets to execute your program. The NoClassDefFoundError indicates that the classloader (in this case java.net.URLClassLoader), which is responsible for dynamically loading classes, cannot find the .class file for the class that you’re trying to use. Your code … Read more