DZone
Java Zone
Thanks for visiting DZone today,
Edit Profile
  • Manage Email Subscriptions
  • How to Post to DZone
  • Article Submission Guidelines
Sign Out View Profile
  • Post an Article
  • Manage My Drafts
Over 2 million developers have joined DZone.
Log In / Join
  • Refcardz
  • Trend Reports
  • Webinars
  • Zones
  • |
    • Agile
    • AI
    • Big Data
    • Cloud
    • Database
    • DevOps
    • Integration
    • IoT
    • Java
    • Microservices
    • Open Source
    • Performance
    • Security
    • Web Dev
DZone > Java Zone > Using Java 7 to target much older JVMs

Using Java 7 to target much older JVMs

Peter Lawrey user avatar by
Peter Lawrey
·
Feb. 15, 12 · Java Zone · Interview
Like (0)
Save
Tweet
12.95K Views

Join the DZone community and get the full member experience.

Join For Free

Java 5.0 and 6 used to have poor support for compiling classes to target older versions of Java. It always supported the previous version, but often no more.

Even if you could compile for previous version, you had to be careful not to use functionality which did exist in the previous versions.

Java 7

Java 7 addresses both these issues. Firstly, it supports sources back to 1.2 and targets back to Java 1.1. Secondly. it insists you set the bootclasspath so you can include the version of the libraries you will be using for that version.
public class Main {
    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}

$ javac -target 1.7 -source 1.7 Main.java
$ javac -target 1.6 -source 1.6 Main.java
warning: [options] bootstrap class path not set in conjunction with -source 1.6
1 warning
$ javac -Xbootclasspath:/usr/java/jdk1.6.0_29/jre/lib/rt.jar -target 1.6 -source 1.6 Main.java
$ javac -Xbootclasspath:/usr/java/jdk1.5.0_22/jre/lib/rt.jar -target 1.5 -source 1.5 Main.java
$ javac -Xbootclasspath:/usr/java/jdk1.4.0_30/jre/lib/rt.jar -target 1.4 -source 1.4 Main.java
$ javac -Xbootclasspath:/usr/java/jdk1.3.1_29/jre/lib/rt.jar -target 1.3 -source 1.3 Main.java
$ javac -Xbootclasspath:/usr/java/jdk1.2.2_017/jre/lib/rt.jar -target 1.2 -source 1.2 Main.java
$ javac -Xbootclasspath:/usr/java/jdk1.1.8_16/jre/lib/rt.jar -target 1.1 -source 1.2 Main.java
$ javac -Xbootclasspath:/usr/java/jdk1.1.8_16/jre/lib/rt.jar -target 1.1 -source 1.1 Main.java
javac: invalid source release: 1.1
Usage: javac  <source>
use -help for a list of possible options
$ javac -Xbootclasspath:/usr/java/jdk1.1.8_16/jre/lib/rt.jar -target 1.0 -source 1.0 Main.java
javac: invalid target release: 1.0
Usage: javac  <source>
use -help for a list of possible options

BTW: All the previous versions back to 1.1 are available from the Oracle web site Oracle Java Archive

 

From http://vanillajava.blogspot.com/2012/02/using-java-7-to-target-much-older-jvms.html

Java (programming language)

Opinions expressed by DZone contributors are their own.

Popular on DZone

  • Blocking Ads on Your Network Using Raspberry Pi 3 + Fedora + Pi-hole
  • What Emerging Technologies Make Data Centers More Energy Efficient?
  • ETL/ELT on Kubernetes With Airbyte
  • How to Build Microservices With Node.js

Comments

Java Partner Resources

X

ABOUT US

  • About DZone
  • Send feedback
  • Careers
  • Sitemap

ADVERTISE

  • Advertise with DZone

CONTRIBUTE ON DZONE

  • Article Submission Guidelines
  • MVB Program
  • Become a Contributor
  • Visit the Writers' Zone

LEGAL

  • Terms of Service
  • Privacy Policy

CONTACT US

  • 600 Park Offices Drive
  • Suite 300
  • Durham, NC 27709
  • support@dzone.com
  • +1 (919) 678-0300

Let's be friends:

DZone.com is powered by 

AnswerHub logo