diff --git a/core-java/src/main/java/com/baeldung/gc/VerboseGarbageCollectorRunner.java b/core-java/src/main/java/com/baeldung/gc/VerboseGarbageCollectorRunner.java new file mode 100644 index 0000000000..f57580bbb5 --- /dev/null +++ b/core-java/src/main/java/com/baeldung/gc/VerboseGarbageCollectorRunner.java @@ -0,0 +1,63 @@ +package com.baeldung.gc; + +import java.util.HashMap; +import java.util.Map; + +/** + * A simple Java program to demonstrate how to enable verbose Garbage Collection (GC) logging. + *

+ * This simple program loads 3 million {@link java.lang.String} instances into a {@link java.util.HashMap} + * object before making an explicit call to the garbage collector using System.gc(). + *

+ * Finally, it removes 2 million of the {@link java.lang.String} instances from the {@link java.util.HashMap}. + * We also explicitly use System.out.println to make interpreting the output easier. + *

+ * Run this program with the following arguments to see verbose GC logging in its complete form: + *

+ * -XX:+UseSerialGC -Xms1024m -Xmx1024m -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xloggc:/path/to/file/gc.log
+ * 
+ * Where: + * + *

+ * It should be noted that the first three arguments are not strictly necessary but for the purposes or the example + * help really simplify things. + * + */ +public class VerboseGarbageCollectorRunner { + + private static Map stringContainer = new HashMap<>(); + + public static void main(String[] args) { + System.out.println("Start of program!"); + String stringWithPrefix = "stringWithPrefix"; + + // Load Java Heap with 3 M java.lang.String instances + for (int i = 0; i < 3000000; i++) { + String newString = stringWithPrefix + i; + stringContainer.put(newString, newString); + } + System.out.println("MAP size: " + stringContainer.size()); + + // Explicit GC! + System.gc(); + + // Remove 2 M out of 3 M + for (int i = 0; i < 2000000; i++) { + String newString = stringWithPrefix + i; + stringContainer.remove(newString); + } + + System.out.println("MAP size: " + stringContainer.size()); + System.out.println("End of program!"); + } + +}