The Java(tm) FAQ -- Input, Output, and Network

Copyright        Table of Contents        Chapters:   1   2   3   4   5   6   7   8   9   10   11

Outline

Basic Input and Output

Q10.1
How do I read a line of input at a time?

ReadLineExample.html, ReadLine11Example.html

See also: Q10.3

Q10.2
How do I read input from the user (or send output) analogous to using standard input and standard output in C or C++?

StandardInputOutputExample.html, StandardInputOutput11Example.html

See also: Q10.1, Q10.3, Q10.4, Q10.5

Q10.3
Why do I get garbage results when I use DataInputStream's readInt or readFloat methods to read in a number from an input string?

ReadIntExample.html

See also: Q10.1

Q10.4
Is there a standard way to read in int, long, float, and double values from a string representation?

ReadNumberExample.html, ReadNumber11Example.html

See also: Q4.19

Q10.5
When do I need to flush an output stream?

See also: Q10.2

Q10.6
Why do I see no output when I run a simple process, such as r.exec("/usr/bin/ls")?

ProcessOutputExample.html, ProcessOutput11Example.html

See also: Q10.2

URL Connections

Q10.7
What's the difference between a URL instance and a URLConnection instance?
Q10.8
How do I make a connection to a URL?

URLConnectionExample.html

See also: Q2.23, Q2.24, Q10.9

Q10.9
How do I read from a remote file if I have its URL?

ReadFromURLExample.html, ReadFromURLAppletExample.html

See also: Q10.1, Q10.2, Q10.6

Q10.10
Why do I get a null result when I use the getHeader... methods in the URLConnection class?

GetHeaderExample.html

Q10.11
What is URLConnection's getOutputStream method intended to work with on the server side?

See also: Q10.12

Q10.12
How do I send data from my Java program to a CGI program?

PostExample.html

See also: Q10.8

Q10.13
Can I write (from my applet) to an external file on a URL?

See also: Q10.12, Q10.13

Q10.14
How can my Java stand-alone application fetch documents in the same fashion as (partially simulating) a browser?

See also: Q10.9

Q10.15
Why do I get a security exception when I try to connect to an external URL from an applet? (If I run equivalent code as an application, it works fine.)

Internet Addresses

Q10.16
The API doesn't list any constructors for InetAddress -- how do I create an InetAddress instance?

InetAddressExample.html

See also: Q1.6, Q1.7, Q2.23

Q10.17
Is it possible to get the real local host IP?

LocalHostExample.html

See also: Q10.16

Q10.18
How can I create an InetAddress instance from an IP address that has no DNS entry?

See also: Q10.16, Q10.20, Q10.27

Sockets

Q10.19
How do I create and use sockets in Java?

SocketExample.html, Socket11Example.html

See also: Q10.3

Q10.20
How can I get a server socket and client socket going on a stand-alone machine, not on a network?

SocketWithoutNetworkExample.html, SocketWithoutNetwork11Example.html

See also: Q10.19

Q10.21
Will raw sockets ever be introduced -- and if not, how can I create ICMP messages so that I can do operations like `ping'?
Q10.22
How do I detect if an input stream belonging to a socket has been terminated by the remote host?

See also: Q10.19

Q10.23
If the Socket class has no support for firewalls, how can I get my Java program with sockets to work through different firewalls?

See also: Q10.19

Q10.24
How do I create a nonblocking server socket in Java?

NonblockingServerExample.html, NonblockingServer11Example.html

See also: Q10.19

Q10.25
Is there a standard Java way to specify the address of the host doing the listening when instantiating a ServerSocket?

See also: Q10.19, Q10.24

Q10.26
How do I send and/or receive datagram packets?

DatagramExample.html

See also: Q10.19

Q10.27
When will I be able to create a broadcast datagram packet?

BroadcastExample.html

See also: Q10.18, Q10.26