Java

Runtime Commands

Run Java applications with the java command. Configure JVM options, memory settings, garbage collectors, and system properties for optimal performance.

9 commands

Pro Tips

Set -Xms and -Xmx to the same value to avoid heap resizing overhead in production.

Use '-XX:+UseG1GC' for balanced throughput and latency in most applications.

Enable '-XX:+HeapDumpOnOutOfMemoryError' to diagnose memory issues in production.

Common Mistakes

Never set heap size larger than available physical memory to avoid system instability.

Avoid using deprecated GC options - check release notes when upgrading Java versions.

Commands

Run Java class

$ java MyClass

Run a compiled Java class with main method.

Run with classpath

$ java -cp lib/*:target/classes com.example.Main

Run with specified classpath including JARs.

Set heap memory

$ java -Xms512m -Xmx4g MyApp

Set initial (512MB) and max (4GB) heap memory.

Use G1 garbage collector

$ java -XX:+UseG1GC MyApp

Run with G1 garbage collector for balanced performance.

Enable heap dump on OOM

$ java -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/tmp MyApp

Automatically create heap dump when OutOfMemoryError occurs.

Set system property

$ java -Dconfig.file=/path/to/config.yml MyApp

Pass system property to the application.

Enable GC logging

$ java -Xlog:gc*:file=gc.log:time,level,tags MyApp

Log garbage collection events to file (Java 9+).

Run single-file source

$ java MyScript.java

Compile and run single-file program directly (Java 11+).

Use ZGC collector

$ java -XX:+UseZGC -Xmx16g MyApp

Use ZGC for low-latency large heap applications.