cd /usr/local
tar -xvzf jdk-21_linux-x64_bin.tar.gz 
rm -rf   jdk-21_linux-x64_bin.tar.gz 
mv /usr/local/jdk-21/ /usr/local/jdk21

#  增加内容
cat >> /etc/profile << EOF
export JAVA_HOME=/usr/local/jdk21
export PATH=$JAVA_HOME/bin:$PATH
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
EOF

source /etc/profile