Java-取出物件memory大小

import org.apache.lucene.util.RamUsageEstimator;


String b = "hello warld!";
System.out.printf("sizeOf(String) = %s bytes\n", 

RamUsageEstimator.sizeOf(b)); 

//pom.xml 新增jar
<dependency>
<groupId>fakepath</groupId>
<artifactId>lucene-core</artifactId>
<version>4.2.0</version>
</dependency>