今天我在JLS的3.10.1 (integer literals)部分偶然发现了这个看似奇怪的陈述:
允许下划线作为表示整数的数字之间的分隔符。
请注意以下内容完全有效(example):
int x = 1_2_3_4_5____6;
下划线只能在数字之间显示,前导/尾随下划线无效。
这是什么理由?是否有一些其他语言的保留?有些风格在当时很常见吗?允许这似乎是一件很奇怪的事情。
答案 0 :(得分:3)
这背后的想法是能够显示一个易于阅读的大数字。
示例: <?php
header("Access-Control-Allow-Origin: *");
?>
<!DOCTYPE html>
<html>
<head>
<title>IO Chat</title>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/1.7.3/socket.io.js"></script>
<script src="jquery.js"></script>
<script>
$.ajax({
url: "sampleclickinggame.esy.es",
type: method,
// This is the important part
xhrFields: {
withCredentials: true
},
// This is the important part
data: data,
success: function (response) {
// handle the response
},
error: function (xhr, status) {
// handle errors
}
});
</script>
<style>
body{
margin-top: 30px;
}
#messageArea{
display: none;
}
</style>
</head>
<body>
<div class="container">
<div id="userFormArea" class="row">
<div class="col-md-12">
<form id="userForm">
<div class="form-group">
<label>Enter UserName</label>
<input class="form-control" id="username" />
<br />
<input type="submit" class="btn btn-primary" value="Login" />
</div>
</form>
</div>
</div>
<div id="messageArea" class="row">
<div class="col-md-4">
<div class="well">
<h3>Online Users</h3>
<ul class="list-group" id="users"></ul>
</div>
</div>
<div class="col-md-8">
<div class="chat" id="chat"></div>
<form id="messageForm">
<div class="form-group">
<label>Enter Message</label>
<textarea class="form-control" id="message"></textarea>
<br />
<input type="submit" class="btn btn-primary" value="Send Message" />
</div>
</form>
</div>
</div>
</div>
<script>
$(function(){
var socket = io.connect();
var $messageForm = $('#messageForm');
var $message = $('#message');
var $chat = $('#chat');
var $messageArea = $('#messageArea');
var $userFormArea = $('#userFormArea');
var $userForm = $('#userForm');
var $users = $('#users');
var $username = $('#username');
$messageForm.submit(function(e){
e.preventDefault();
socket.emit('send message', $message.val());
$message.val('');
});
socket.on('new message', function(data){
$chat.append('<div class="well"><strong>'+data.user+'</strong>: '+data.msg+'</div>');
});
$userForm.submit(function(e){
e.preventDefault();
socket.emit('new user', $username.val(), function(data){
if(data){
$userFormArea.hide();
$messageArea.show();
}
});
$username.val('');
});
socket.on('get users', function(data){
var html = '';
for(var i = 0;i < data.length;i++){
html += '<li class="list-group-item">'+data[i]+'</li>';
}
$users.html(html);
});
});
</script>
</body>
</html>
还有其他用例,但这是我认为最常用的。
有关详细信息,请参阅the documentation。