How to Install and Switch Between Multiple JDKs on Windows

Overview

The author describes a practical setup for running both Java 7 and Java 8 on a single Windows machine. The need arises from a new project requiring Java 7 while an existing environment uses Java 8.

Prerequisites

Download the desired JDK versions from Oracle's official website or a trusted historical archive. The author references a blog post for downloading older versions: "从官网下载历史版本的java - DbWong_0918 - 博客园 (cnblogs.com)".

Installation Directories

The example installation paths used in this guide are:

Java 7: C:\Program Files\Java\jdk1.7.0_80 Java 8:

C:\Program Files\Java\jdk1.8.0_291

Environment Variable Configuration

Create two system variables, one for each JDK version: JAVA_HOME7 =

C:\Program Files\Java\jdk1.7.0_80

JAVA_HOME8

= C:\Program Files\Java\jdk1.8.0_291 Then create a master JAVA_HOME variable that points to the desired version by referencing the corresponding version-specific variable. For example, to use Java 7, set JAVA_HOME to %JAVA_HOME7%.

Set the CLASSPATH variable to: .;%JAVA_HOME%\lib;%JAVA_HOME%\lib\tools.jar Update the system PATH variable: remove any existing %JAVA_HOME% entries and prepend the following entries so they take precedence: %JAVA_HOME%\bin;%JAVA_HOME%\jre\bin; Place these entries at the very top of the PATH list.

Remove System-Wide Java Executables

Navigate to C:\Windows\System32 and delete java.exe, javaw.exe, and javaws.exe. This prevents the system from using a globally installed Java version that could conflict with the version selected via JAVA_HOME.

Verification

Open a new Command Prompt window and run: java -version The output should display the version corresponding to the currently active JAVA_HOME (e.g., Java 7).

Reference Screenshot