Performance optimization for Java programs

Program | performance | Optimization

1 using non-blocking I/O

The less-than-version JDK does not support non-blocking I/O APIs. To avoid I/O blocking, some applications use a method of creating a large number of threads (in better cases, a buffer pool is used). This technique can be seen in a number of applications that must support concurrent I/O flows, such as Web servers, quotes, and auction applications. However, creating a Java thread requires considerable overhead.

JDK 1.4 introduces a non-blocking I/O library (Java.nio). If the application requires the use of an older JDK, there is a package that supports non-blocking I/O.

2 cautious use of abnormal

Exceptions are bad for performance. Throwing an exception begins by creating a new object. The constructor of the Throwable interface calls the local (Native) method named Fillinstacktrace (), and the Fillinstacktrace () method checks the stack to collect call tracking information. Whenever an exception is thrown, the VM must adjust the call stack because a new object is created during the process.

Exceptions can only be used for error handling and should not be used to control the process.

3 do not repeat initialization of variables

By default, when the constructor of a class is invoked, Java initializes the variable to the determined value: All objects are set to NULL, the integer variable (byte, short, int, long) is set to 0,float and the double variable is set to 0.0, and the logical value is set to False. This should be especially noted when a class derives from another class, because when an object is created with the new keyword, all constructors in the chain of the constructor are invoked automatically.

4 Specify the final modifier for the class as much as possible

A class with the final modifier is not derived. In the Java Core API, there are many examples of final application, such as java.lang.String. Specifying final for the string class prevents people from overwriting the length () method.

In addition, if you specify that a class is final, all methods of that class are final. The Java compiler looks for the opportunity to inline (inline) all final methods (this is related to the specific compiler implementation). This will increase performance by an average of 50%.

5 use local variables as much as possible

The parameters passed when the method is invoked and the temporary variables created in the call are saved in the stack (stack) faster. Other variables, such as static variables, instance variables, and so on, are created in the heap (Heap) in a slower speed. In addition, local variables may be further optimized depending on the specific compiler/JVM.