Found 74 Articles for Java Technologies

There is no global variables support in Java. Static variables can be used as an alternate solution for global variables.

Class variables also known as static variables are declared with the static keyword in a class, but outside a method, constructor or a block. There would only be one copy of each class variable per class, regardless of how many objects are created from it. Static variables are rarely used other than being declared as constants. Constants are variables that are declared as public/private, final, and static. Constant variables never change from ... Read More

Instance variables are declared in a class, but outside a method, constructor or any block.When space is allocated for an object in the heap, a slot for each instance variable value is created.Instance variables are created when an object is created with the use of the keyword 'new' and destroyed when the object is destroyed.Instance variables hold values that must be referenced by more than one method, constructor or block, or essential parts of an object's state that must be present throughout the class.Instance variables can be declared at the class level before or after use.Access modifiers can be given ... Read More

Local VariableLocal variables are declared in methods, constructors, or blocks.Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor, or block.Access modifiers cannot be used for local variables.Local variables are visible only within the declared method, constructor, or block.Local variables are implemented at stack level internally.There is no default value for local variables, so local variables should be declared and an initial value should be assigned before the first use.Instance/Member VariableInstance variables are declared in a class, but outside a method, constructor or any block.When a ... Read More

Member variables are known as instance variables in java.Instance variables are declared in a class, but outside a method, constructor or any block.When space is allocated for an object in the heap, a slot for each instance variable value is created.Instance variables are created when an object is created with the use of the keyword 'new' and destroyed when the object is destroyed.Instance variables hold values that must be referenced by more than one method, constructor or block, or essential parts of an object's state that must be present throughout the class.Instance variables can be declared in a class level ... Read More

Local variables are declared in methods, constructors, or blocks.Local variables are created when the method, constructor or block is entered and the variable will be destroyed once it exits the method, constructor, or block.Access modifiers cannot be used for local variables.Local variables are visible only within the declared method, constructor, or block.Local variables are implemented at stack level internally.There is no default value for local variables, so local variables should be declared and an initial value should be assigned before the first use.ExampleHere, age is a local variable. This is defined inside pupAge()method and its scope is limited to only ... Read More

All Java components require names. Names used for classes, variables, and methods are called identifiers. In Java, there are several points to remember about identifiers. They are as follows - Step 1 − All identifiers should begin with a letter (A to Z or a to z), currency character ($) or an underscore (_). Step 2 − After the first character, identifiers can have any combination of characters. Step 3 − A keyword cannot be used as an identifier. Step 4 − Most importantly, identifiers are case sensitive. Step 5 − Examples of legal identifiers: age, $salary, _value, __1_value. Step 6 − Examples of illegal identifiers: 123abc, -salary.

Following steps are mostly required to Troubleshoot any problem that occurred in production.As the first step, get the time frame from the user when a particular issue occurred. Get the logs for that particular time period.If logs are very large in size, use grep command to filter out errors.$ grep -o "\w*Exception" error.log | sort -r | uniq -cIt will help to get all the exceptions in error.log sorted in reversed order and give the unique result and with counts.

Following are the areas where Java has proved itself faster than C++.Memory allocation/deallocation: Memory allocation/deallocation is much faster and it is often faster to create a new big array instead of using the cached one.Object instantiation: Memory management done by GC of Java attributes faster object related operations on Java than C++.Multithreading and Synchronization: Modern Java programs makes use of multi-core systems to make synchronization and multithreading much faster operation.JIT has improved a lot over period of time and modern Java program execution now is much faster.String operations are faster by having length. Collection methods are optimized like Array copy.Class loading ... Read More

Modern Java is quite fast and is comparable to C++ code base but it still takes lot of memory. Slowness of Java programs is primarily because of bad programming practices. But following areas are where Java can be improved.Java libraries are written keeping readability and correctness in mind, not performance.Slow String based operations as Strings are UTF-16 encoded objects and are immutable. So more String are used, more memory is required.Boundary checks on arrays also make its operations bit slow.I/O Stream operations are slow considering synchronization checks on each access.Lacking low level functionality like C also attributes to slowness in ... Read More