1、Ubuntu 下搜索jdk安装位置
which javac 返回/usr/bin/javac file /usr/bin/javac 返回/usr/bin/javac: symbolic link to `/etc/alternatives/javac' 然后file /etc/alternatives/javac 返回/etc/alternatives/javac: symbolic link to `/usr/lib/jvm/java-6-sun/bin/javac' 然后file /usr/lib/jvm/java-6-sun/bin/javac 返回/usr/lib/jvm/java-6-sun/bin/javac: ELF 32-bit LSB executable,Intel 80386,version 1 (SYSV),dynamically linked (uses shared libs),for GNU/Linux 2.2.5,not stripped 到此为止，说明路径是/usr/lib/jvm/java-6-sun/bin/
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