During the Java development process, fine configuration of the startup parameters of the Java virtual machine (JVM) is an important means to improve application performance and stability. Next, we will dive into the three common options -D, -X and -XX in the JVM startup parameters to better understand their role in JVM startup and operation.
1. -D parameters
The -D parameter is used to set system properties, which allows you to specify a key-value pair when JVM starts, where the key is the attribute name and the value is the attribute value. These system properties can be obtained using methods in Java applications. The syntax format of the -D parameter is as follows:
-Dkey=value
For example, the following command line will set the property value named "myprop" to "myvalue":
java -Dmyprop=myvalue MyApp
In the application, you can use the following code to get the value of the property:
String myPropValue = (“myprop”);
II. -X parameters
-X parameters are used to set specific parameters of the JVM that are not part of the Java application but are used to configure the behavior of the JVM. -X parameters are usually used to adjust the performance and memory settings of the JVM. Unlike the -D parameter, the syntax format of the -X parameter is relatively simple, usually:
-Xoption
For example, the following command line will set the size of heap memory to 1024MB:
java -Xms1024m MyApp
Here, "-Xms" is a -X parameter that sets the initial size of the JVM heap memory. Similarly, there is also the "-Xmx" parameter to set the maximum size of heap memory.
III. -XX parameters
-XX parameter is a debug and advanced configuration option for JVM, for deeper control of the behavior and performance of the JVM. These parameters are usually only used during the development or debugging phase, as they may have an impact on the performance of the application. The syntax format of the -XX parameter is as follows:
-XX:option=value
For example, the following command line will enable garbage collection logging:
java -XX:+PrintGCDetails MyApp
Here, "-XX:+PrintGCDetails" is a -XX parameter used to enable detailed logging of garbage collection. There are many other -XX parameters that can be used to adjust the behavior of the JVM memory management, JIT compiler optimization, etc.
Summarize:
-D, -X, and -XX are three common options in JVM startup parameters, which have different uses and functions. The -D parameter is used to set system properties and can be obtained using methods in the application; the -X parameter is used to configure the behavior of the JVM, such as adjusting the heap memory size; the -XX parameter is used to further control the behavior and performance of the JVM, and is usually only used in the development or debugging stage. Understanding the differences and uses of these parameters will help better optimize the performance of the JVM and meet the needs of the application. In practical applications, appropriate parameter options should be selected according to specific needs and scenarios to achieve optimal performance and results. At the same time, with the help of auxiliary tools such as Baidu Smart Cloud Xinkuai Code (Comate), the efficiency of code writing and optimization can be further improved.
Others:-server
The -server option is used to start a Java virtual machine (JVM) for server-side applications. It enables more advanced compilation optimization and more memory management to provide better server-side performance.
To start a Java program on the command line and use the -server option, you can do this:
java -server -jar
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