查看环境(centos7.5):cat /etc/redhat-release
查看所有安装了的java, 关键字是java ,-qa 显示所有安装
删除软件, -e erase 擦除的首字母, --nodeps 双杠,即使有依赖也强行删除
官网下载jdk需要登录,账号2696671285@qq.com ,密码Oracle123;或推荐在下载链接右键选择“使用迅雷下载”,可以不用登录
解压:tar -zxvf jdk-8u181-linux-x64.tar.gz
移动:cp -r jdk1.8.0_181/ /usr/java1.8
配置环境变量:vi /etc/profile,在文件最后添加如下内容:
# java environment
export JAVA_HOME=/usr/java1.8
export CLASSPATH=.:${JAVA_HOME}/jre/lib/rt.jar:${JAVA_HOME}/lib/dt.jar:${JAVA_HOME}/lib/tools.jar
export PATH=$PATH:${JAVA_HOME}/bin
使配置文件生效:source /etc/profile
查看环境变量:echo $CLASSPATH
/root/java目录创建测试代码Server.java和Client.java:
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class Server {
//server程序
public static void main(String[] args) {
try {
ServerSocket ss = new ServerSocket(3113);
Socket s = ss.accept();
InputStream is = s.getInputStream();
byte[] buf =new byte[1024];
int len = is.read(buf);
System.out.println("recv:"+new String(buf,0,len));
Thread.sleep(10000);
s.getOutputStream().write("hello".getBytes());
System.out.println("send over");
System.in.read();
}catch (Exception e){
e.printStackTrace();
}
}
}
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.Socket;
public class Client {
//client程序
public static void main(String[] args) {
try {
Socket s = new Socket();
s.setSoLinger(true,0);//设置调用close就发送RST
s.connect(new InetSocketAddress("127.0.0.1",3113));
OutputStream os = s.getOutputStream();
os.write("hello".getBytes());
s.close();
System.in.read();//防止程序退出
}catch (Exception e){
e.printStackTrace();
}
}
}
注意不要package,执行javac Server.java && java Server,另起一个终端运行javac Client.java && java Client,运行成功,执行jps查看。
(或在/root/java/test里面创建类Xxx,package test;然后在/root/java里执行java test.Xxx也可以,否则会报错:Error: Could not find or load main class)