安装JDK 9与使用jshell

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安装JDK 9与使用jshell

1、下载JDK9

http://www.oracle.com/technetwork/java/javase/downloads/jdk9-downloads-3848520.html

2、安装JDK9

3、配置环境变量

4、进入命令行，查看Java版本

5、启动交互式jshell

文件读写操作：

shell> File file = new File("d:/test.txt")
        file ==> d:\test.txt
         
        jshell> file.createNewFile()
        $12 ==> true
         
        jshell> FileWriter fw = new FileWriter(file)
        fw ==> java.io.FileWriter@53f65459
         
        jshell> fw.write("I love Java.\nI learn Java.\nLet's learn Java.")
         
        jshell> fw.close()
         
        jshell> FileReader fr = new FileReader(file)
        fr ==> java.io.FileReader@4d50efb8
         
        jshell> BufferedReader br = new BufferedReader(fr)
        br ==> java.io.BufferedReader@7e2d773b
         
        jshell> String nextLine = ""
        nextLine ==> ""
         
        jshell> while ((nextLine = br.readLine()) != null) {
           ...>      System.out.println(nextLine);
           ...> }
        I love Java.
        I learn Java.
        Let's learn Java.

可以看出，单行的Java语句省掉分号结束符是可以的，但是在循环结构里的System.out.println(nextLine); 分号就是不能省掉的。

流操作：

jshell> List lines = Arrays.asList(“howard”, “mike”, “smith”, “alice”, “gree”) ");
lines ==> [howard, mike, smith, alice, green]
jshell> lines.stream().filter(x -> x.contains(“m”)).forEach(System.out::println);
mike
smith