From 8d0a2e6b79533856e82a8541b5b866ebd6fdeb4e Mon Sep 17 00:00:00 2001
From: hanguokai <han.guokai@gmail.com>
Date: Sat, 10 Aug 2013 06:31:51 +0800
Subject: add translation for dart.

---
 zh-cn/dart-cn.html.markdown | 509 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 509 insertions(+)
 create mode 100644 zh-cn/dart-cn.html.markdown

(limited to 'zh-cn/dart-cn.html.markdown')

diff --git a/zh-cn/dart-cn.html.markdown b/zh-cn/dart-cn.html.markdown
new file mode 100644
index 00000000..47b1a93b
--- /dev/null
+++ b/zh-cn/dart-cn.html.markdown
@@ -0,0 +1,509 @@
+---
+language: dart
+filename: learndart.dart
+contributors:
+    - ["Joao Pedrosa", "https://github.com/jpedrosa/"]
+translators:
+    - ["Guokai Han", "https://github.com/hanguokai/"]
+---
+
+Dart 是编程语言王国的新人。
+它借鉴了许多其他主流语言，并且不会偏离它的兄弟语言 JavaScript 太多。
+就像 JavaScript，Dart 的目标是提供良好的浏览器集成。
+
+Dart 最有争议的特性必然是它的可选类型。
+
+```javascript
+import "dart:collection";
+import "dart:math" as DM;
+
+// Welcome to Learn Dart in 15 minutes. http://www.dartlang.org/
+// This is an executable tutorial. You can run it with Dart or on
+// the Try Dart! site if you copy/paste it there. http://try.dartlang.org/
+
+// Function declaration and method declaration look the same. Function
+// declarations can be nested. The declaration takes the form of
+// name() {} or name() => singleLineExpression;
+// The fat arrow function declaration has an implicit return for the result of
+// the expression.
+example1() {
+  example1nested1() {
+    example1nested2() => print("Example1 nested 1 nested 2");
+    example1nested2();
+  }
+  example1nested1();
+}
+
+// Anonymous functions don't include a name.
+example2() {
+  example2nested1(fn) {
+    fn();
+  }
+  example2nested1(() => print("Example2 nested 1"));
+}
+
+// When a function parameter is declared, the declaration can include the
+// number of parameters the function takes by specifying the names of the
+// parameters it takes.
+example3() {
+  example3nested1(fn(informSomething)) {
+    fn("Example3 nested 1");
+  }
+  example3planB(fn) { // Or don't declare number of parameters.
+    fn("Example3 plan B");
+  }
+  example3nested1((s) => print(s));
+  example3planB((s) => print(s));
+}
+
+// Functions have closure access to outer variables.
+var example4Something = "Example4 nested 1";
+example4() {
+  example4nested1(fn(informSomething)) {
+    fn(example4Something);
+  }
+  example4nested1((s) => print(s));
+}
+
+// Class declaration with a sayIt method, which also has closure access
+// to the outer variable as though it were a function as seen before.
+var example5method = "Example5 sayIt";
+class Example5Class {
+  sayIt() {
+    print(example5method);
+  }
+}
+example5() {
+  // Create an anonymous instance of the Example5Class and call the sayIt
+  // method on it.
+  new Example5Class().sayIt();
+}
+
+// Class declaration takes the form of class name { [classBody] }.
+// Where classBody can include instance methods and variables, but also
+// class methods and variables.
+class Example6Class {
+  var example6InstanceVariable = "Example6 instance variable"; 
+  sayIt() {
+    print(example6InstanceVariable);
+  }
+}
+example6() {
+  new Example6Class().sayIt();
+}
+
+// Class methods and variables are declared with "static" terms.
+class Example7Class {
+  static var example7ClassVariable = "Example7 class variable"; 
+  static sayItFromClass() {
+    print(example7ClassVariable);
+  }
+  sayItFromInstance() {
+    print(example7ClassVariable);
+  }
+}
+example7() {
+  Example7Class.sayItFromClass();
+  new Example7Class().sayItFromInstance();
+}
+
+// Literals are great, but there's a restriction for what literals can be
+// outside of function/method bodies. Literals on the outer scope of class
+// or outside of class have to be constant. Strings and numbers are constant
+// by default. But arrays and maps are not. They can be made constant by
+// declaring them "const".
+var example8A = const ["Example8 const array"],
+  example8M = const {"someKey": "Example8 const map"}; 
+example8() {
+  print(example8A[0]);
+  print(example8M["someKey"]);
+}
+
+// Loops in Dart take the form of standard for () {} or while () {} loops,
+// slightly more modern for (.. in ..) {}, or functional callbacks with many
+// supported features, starting with forEach.
+var example9A = const ["a", "b"];
+example9() {
+  for (var i = 0; i < example9A.length; i++) {
+    print("Example9 for loop '${example9A[i]}'");
+  }
+  var i = 0;
+  while (i < example9A.length) {
+    print("Example9 while loop '${example9A[i]}'");
+    i++;
+  }
+  for (var e in example9A) {
+    print("Example9 for-in loop '${e}'");
+  }
+  example9A.forEach((e) => print("Example9 forEach loop '${e}'"));
+}
+
+// To loop over the characters of a string or to extract a substring.
+var example10S = "ab";
+example10() {
+  for (var i = 0; i < example10S.length; i++) {
+    print("Example10 String character loop '${example10S[i]}'");
+  }
+  for (var i = 0; i < example10S.length; i++) {
+    print("Example10 substring loop '${example10S.substring(i, i + 1)}'");
+  }
+}
+
+// Int and double are the two supported number formats.
+example11() {
+  var i = 1 + 320, d = 3.2 + 0.01;
+  print("Example11 int ${i}");
+  print("Example11 double ${d}");
+}
+
+// DateTime provides date/time arithmetic.
+example12() {
+  var now = new DateTime.now();
+  print("Example12 now '${now}'");
+  now = now.add(new Duration(days: 1));
+  print("Example12 tomorrow '${now}'");
+}
+
+// Regular expressions are supported.
+example13() {
+  var s1 = "some string", s2 = "some", re = new RegExp("^s.+?g\$");
+  match(s) {
+    if (re.hasMatch(s)) {
+      print("Example13 regexp matches '${s}'");
+    } else {
+      print("Example13 regexp doesn't match '${s}'");
+    }
+  }
+  match(s1);
+  match(s2);
+}
+
+// Boolean expressions need to resolve to either true or false, as no
+// implicit conversions are supported.
+example14() {
+  var v = true;
+  if (v) {
+    print("Example14 value is true");
+  }
+  v = null;
+  try {
+    if (v) {
+      // Never runs
+    } else {
+      // Never runs
+    }
+  } catch (e) {
+    print("Example14 null value causes an exception: '${e}'");
+  }
+}
+
+// try/catch/finally and throw are used for exception handling.
+// throw takes any object as parameter;
+example15() {
+  try {
+    try {
+      throw "Some unexpected error.";
+    } catch (e) {
+      print("Example15 an exception: '${e}'");
+      throw e; // Re-throw
+    }
+  } catch (e) {
+    print("Example15 catch exception being re-thrown: '${e}'");
+  } finally {
+    print("Example15 Still run finally");
+  }
+}
+
+// To be efficient when creating a long string dynamically, use
+// StringBuffer. Or you could join a string array.
+example16() {
+  var sb = new StringBuffer(), a = ["a", "b", "c", "d"], e;
+  for (e in a) { sb.write(e); }
+  print("Example16 dynamic string created with "
+    "StringBuffer '${sb.toString()}'");
+  print("Example16 join string array '${a.join()}'");
+}
+
+// Strings can be concatenated by just having string literals next to
+// one another with no further operator needed.
+example17() {
+  print("Example17 "
+      "concatenate "
+      "strings "
+      "just like that");
+}
+
+// Strings have single-quote or double-quote for delimiters with no
+// actual difference between the two. The given flexibility can be good
+// to avoid the need to escape content that matches the delimiter being
+// used. For example, double-quotes of HTML attributes if the string
+// contains HTML content.
+example18() {
+  print('Example18 <a href="etc">'
+      "Don't can't I'm Etc"
+      '</a>');
+}
+
+// Strings with triple single-quotes or triple double-quotes span
+// multiple lines and include line delimiters.
+example19() {
+  print('''Example19 <a href="etc"> 
+Example19 Don't can't I'm Etc
+Example19 </a>''');
+}
+
+// Strings have the nice interpolation feature with the $ character.
+// With $ { [expression] }, the return of the expression is interpolated.
+// $ followed by a variable name interpolates the content of that variable.
+// $ can be escaped like so \$ to just add it to the string instead.
+example20() {
+  var s1 = "'\${s}'", s2 = "'\$s'";
+  print("Example20 \$ interpolation ${s1} or $s2 works.");
+}
+
+// Optional types allow for the annotation of APIs and come to the aid of
+// IDEs so the IDEs can better refactor, auto-complete and check for
+// errors. So far we haven't declared any types and the programs have
+// worked just fine. In fact, types are disregarded during runtime.
+// Types can even be wrong and the program will still be given the
+// benefit of the doubt and be run as though the types didn't matter.
+// There's a runtime parameter that checks for type errors which is
+// the checked mode, which is said to be useful during development time,
+// but which is also slower because of the extra checking and is thus
+// avoided during deployment runtime.
+class Example21 {
+  List<String> _names;
+  Example21() {
+    _names = ["a", "b"]; 
+  }
+  List<String> get names => _names;
+  set names(List<String> list) {
+    _names = list;
+  }
+  int get length => _names.length;
+  void add(String name) {
+    _names.add(name);
+  }
+}
+void example21() {
+  Example21 o = new Example21();
+  o.add("c");
+  print("Example21 names '${o.names}' and length '${o.length}'");
+  o.names = ["d", "e"];
+  print("Example21 names '${o.names}' and length '${o.length}'");
+}
+
+// Class inheritance takes the form of class name extends AnotherClassName {}.
+class Example22A {
+  var _name = "Some Name!";
+  get name => _name;
+}
+class Example22B extends Example22A {}
+example22() {
+  var o = new Example22B();
+  print("Example22 class inheritance '${o.name}'");
+}
+
+// Class mixin is also available, and takes the form of
+// class name extends SomeClass with AnotherClassName {}.
+// It's necessary to extend some class to be able to mixin another one.
+// The template class of mixin cannot at the moment have a constructor.
+// Mixin is mostly used to share methods with distant classes, so the
+// single inheritance doesn't get in the way of reusable code.
+// Mixins follow the "with" statement during the class declaration.
+class Example23A {}
+class Example23Utils {
+  addTwo(n1, n2) {
+    return n1 + n2;
+  }
+}
+class Example23B extends Example23A with Example23Utils {
+  addThree(n1, n2, n3) {
+    return addTwo(n1, n2) + n3;
+  }
+}
+example23() {
+  var o = new Example23B(), r1 = o.addThree(1, 2, 3),
+    r2 = o.addTwo(1, 2);
+  print("Example23 addThree(1, 2, 3) results in '${r1}'");
+  print("Example23 addTwo(1, 2) results in '${r2}'");
+}
+
+// The Class constructor method uses the same name of the class and
+// takes the form of SomeClass() : super() {}, where the ": super()"
+// part is optional and it's used to delegate constant parameters to the
+// super-parent's constructor.
+class Example24A {
+  var _value;
+  Example24A({value: "someValue"}) {
+    _value = value;
+  }
+  get value => _value;
+}
+class Example24B extends Example24A {
+  Example24B({value: "someOtherValue"}) : super(value: value);
+}
+example24() {
+  var o1 = new Example24B(),
+    o2 = new Example24B(value: "evenMore");
+  print("Example24 calling super during constructor '${o1.value}'");
+  print("Example24 calling super during constructor '${o2.value}'");
+}
+
+// There's a shortcut to set constructor parameters in case of simpler classes.
+// Just use the this.parameterName prefix and it will set the parameter on
+// an instance variable of same name.
+class Example25 {
+  var value, anotherValue;
+  Example25({this.value, this.anotherValue});
+}
+example25() {
+  var o = new Example25(value: "a", anotherValue: "b");
+  print("Example25 shortcut for constructor '${o.value}' and "
+    "'${o.anotherValue}'");
+}
+
+// Named parameters are available when declared between {}.
+// Parameter order can be optional when declared between {}.
+// Parameters can be made optional when declared between [].
+example26() {
+  var _name, _surname, _email;
+  setConfig1({name, surname}) {
+    _name = name;
+    _surname = surname;
+  }
+  setConfig2(name, [surname, email]) {
+    _name = name;
+    _surname = surname;
+    _email = email;
+  }
+  setConfig1(surname: "Doe", name: "John");
+  print("Example26 name '${_name}', surname '${_surname}', "
+    "email '${_email}'");
+  setConfig2("Mary", "Jane");
+  print("Example26 name '${_name}', surname '${_surname}', "
+  "email '${_email}'");
+}
+
+// Variables declared with final can only be set once.
+// In case of classes, final instance variables can be set via constant
+// constructor parameter.
+class Example27 {
+  final color1, color2;
+  // A little flexibility to set final instance variables with syntax
+  // that follows the :
+  Example27({this.color1, color2}) : color2 = color2;
+}
+example27() {
+  final color = "orange", o = new Example27(color1: "lilac", color2: "white");
+  print("Example27 color is '${color}'");
+  print("Example27 color is '${o.color1}' and '${o.color2}'");
+}
+
+// To import a library, use import "libraryPath" or if it's a core library,
+// import "dart:libraryName". There's also the "pub" package management with
+// its own convention of import "package:packageName".
+// See import "dart:collection"; at the top. Imports must come before
+// other code declarations. IterableBase comes from dart:collection.
+class Example28 extends IterableBase {
+  var names;
+  Example28() {
+    names = ["a", "b"];
+  }
+  get iterator => names.iterator;
+}
+example28() {
+  var o = new Example28();
+  o.forEach((name) => print("Example28 '${name}'"));
+}
+
+// For control flow we have:
+// * standard switch with must break statements
+// * if-else if-else and ternary ..?..:.. operator
+// * closures and anonymous functions
+// * break, continue and return statements
+example29() {
+  var v = true ? 30 : 60;
+  switch (v) {
+    case 30:
+      print("Example29 switch statement");
+      break;
+  }
+  if (v < 30) {
+  } else if (v > 30) {
+  } else {
+    print("Example29 if-else statement");
+  }
+  callItForMe(fn()) {
+    return fn();
+  }
+  rand() {
+    v = new DM.Random().nextInt(50);
+    return v;
+  }
+  while (true) {
+    print("Example29 callItForMe(rand) '${callItForMe(rand)}'");
+    if (v != 30) {
+      break;
+    } else {
+      continue;
+    }
+    // Never gets here.
+  }
+}
+
+// Parse int, convert double to int, or just keep int when dividing numbers
+// by using the ~/ operation. Let's play a guess game too.
+example30() {
+  var gn, tooHigh = false,
+    n, n2 = (2.0).toInt(), top = int.parse("123") ~/ n2, bottom = 0;
+  top = top ~/ 6;
+  gn = new DM.Random().nextInt(top + 1); // +1 because nextInt top is exclusive
+  print("Example30 Guess a number between 0 and ${top}");
+  guessNumber(i) {
+    if (n == gn) {
+      print("Example30 Guessed right! The number is ${gn}");
+    } else {
+      tooHigh = n > gn;
+      print("Example30 Number ${n} is too "
+        "${tooHigh ? 'high' : 'low'}. Try again");
+    }
+    return n == gn;
+  }
+  n = (top - bottom) ~/ 2;
+  while (!guessNumber(n)) {
+    if (tooHigh) {
+      top = n - 1;
+    } else {
+      bottom = n + 1;
+    }
+    n = bottom + ((top - bottom) ~/ 2);
+  }
+}
+
+// Programs have only one entry point in the main function.
+// Nothing is expected to be executed on the outer scope before a program
+// starts running with what's in its main function.
+// This helps with faster loading and even lazily loading of just what
+// the program needs to startup with.
+main() {
+  print("Learn Dart in 15 minutes!");
+  [example1, example2, example3, example4, example5, example6, example7,
+    example8, example9, example10, example11, example12, example13, example14,
+    example15, example16, example17, example18, example19, example20,
+    example21, example22, example23, example24, example25, example26,
+    example27, example28, example29, example30
+    ].forEach((ef) => ef());
+}
+
+```
+
+## 延伸阅读
+
+Dart 有一个全面的网站。它涵盖了 API 参考、入门向导、文章以及更多，
+包括一个有用的 Dart 在线试用。
+http://www.dartlang.org/
+http://try.dartlang.org/
+
+
+
-- 
cgit v1.2.3


From c5c76b4a5d36b729bd782d3e3695aa1a7083a129 Mon Sep 17 00:00:00 2001
From: hanguokai <han.guokai@gmail.com>
Date: Sat, 10 Aug 2013 06:35:01 +0800
Subject: add translation for dart.

---
 zh-cn/dart-cn.html.markdown | 205 +++++++++++++++++++++-----------------------
 1 file changed, 97 insertions(+), 108 deletions(-)

(limited to 'zh-cn/dart-cn.html.markdown')

diff --git a/zh-cn/dart-cn.html.markdown b/zh-cn/dart-cn.html.markdown
index 47b1a93b..64663b21 100644
--- a/zh-cn/dart-cn.html.markdown
+++ b/zh-cn/dart-cn.html.markdown
@@ -9,7 +9,7 @@ translators:
 
 Dart 是编程语言王国的新人。
 它借鉴了许多其他主流语言，并且不会偏离它的兄弟语言 JavaScript 太多。
-就像 JavaScript，Dart 的目标是提供良好的浏览器集成。
+就像 JavaScript 一样，Dart 的目标是提供良好的浏览器集成。
 
 Dart 最有争议的特性必然是它的可选类型。
 
@@ -17,15 +17,14 @@ Dart 最有争议的特性必然是它的可选类型。
 import "dart:collection";
 import "dart:math" as DM;
 
-// Welcome to Learn Dart in 15 minutes. http://www.dartlang.org/
-// This is an executable tutorial. You can run it with Dart or on
-// the Try Dart! site if you copy/paste it there. http://try.dartlang.org/
+// 欢迎进入15分钟的 Dart 学习。 http://www.dartlang.org/
+// 这是一个可实际执行的向导。你可以用 Dart 运行它
+// 或者在线执行! 可以把代码复制/粘贴到这个网站。 http://try.dartlang.org/
 
-// Function declaration and method declaration look the same. Function
-// declarations can be nested. The declaration takes the form of
-// name() {} or name() => singleLineExpression;
-// The fat arrow function declaration has an implicit return for the result of
-// the expression.
+// 函数声明和方法声明看起来一样。
+// 函数声明可以嵌套。声明使用这种 name() {} 的形式，
+// 或者 name() => 单行表达式; 的形式。
+// 右箭头的声明形式会隐式地返回表达式的结果。
 example1() {
   example1nested1() {
     example1nested2() => print("Example1 nested 1 nested 2");
@@ -34,7 +33,7 @@ example1() {
   example1nested1();
 }
 
-// Anonymous functions don't include a name.
+// 匿名函数没有函数名。
 example2() {
   example2nested1(fn) {
     fn();
@@ -42,21 +41,20 @@ example2() {
   example2nested1(() => print("Example2 nested 1"));
 }
 
-// When a function parameter is declared, the declaration can include the
-// number of parameters the function takes by specifying the names of the
-// parameters it takes.
+// 当声明函数类型的参数的时候，声明中可以包含
+// 函数参数需要的参数，指定所需的参数名即可。
 example3() {
   example3nested1(fn(informSomething)) {
     fn("Example3 nested 1");
   }
-  example3planB(fn) { // Or don't declare number of parameters.
+  example3planB(fn) { // 或者不声明函数参数的参数
     fn("Example3 plan B");
   }
   example3nested1((s) => print(s));
   example3planB((s) => print(s));
 }
 
-// Functions have closure access to outer variables.
+// 函数有可以访问到外层变量的闭包。
 var example4Something = "Example4 nested 1";
 example4() {
   example4nested1(fn(informSomething)) {
@@ -65,8 +63,8 @@ example4() {
   example4nested1((s) => print(s));
 }
 
-// Class declaration with a sayIt method, which also has closure access
-// to the outer variable as though it were a function as seen before.
+// 下面这个包含 sayIt 方法的类声明，同样有一个可以访问外层变量的闭包，
+// 就像前面的函数一样。
 var example5method = "Example5 sayIt";
 class Example5Class {
   sayIt() {
@@ -74,14 +72,14 @@ class Example5Class {
   }
 }
 example5() {
-  // Create an anonymous instance of the Example5Class and call the sayIt
-  // method on it.
+  // 创建一个 Example5Class 类的匿名实例，
+  // 并调用它的 sayIt 方法。
   new Example5Class().sayIt();
 }
 
-// Class declaration takes the form of class name { [classBody] }.
-// Where classBody can include instance methods and variables, but also
-// class methods and variables.
+// 类的声明使用这种形式 class name { [classBody] }.
+// classBody 中可以包含实例方法和变量，
+// 还可以包含类方法和变量。
 class Example6Class {
   var example6InstanceVariable = "Example6 instance variable"; 
   sayIt() {
@@ -92,7 +90,7 @@ example6() {
   new Example6Class().sayIt();
 }
 
-// Class methods and variables are declared with "static" terms.
+// 类方法和变量使用 static 关键词声明。
 class Example7Class {
   static var example7ClassVariable = "Example7 class variable"; 
   static sayItFromClass() {
@@ -107,11 +105,10 @@ example7() {
   new Example7Class().sayItFromInstance();
 }
 
-// Literals are great, but there's a restriction for what literals can be
-// outside of function/method bodies. Literals on the outer scope of class
-// or outside of class have to be constant. Strings and numbers are constant
-// by default. But arrays and maps are not. They can be made constant by
-// declaring them "const".
+// 字面量非常方便，但是对于在函数/方法的外层的字面量有一个限制，
+// 类的外层或外面的字面量必需是常量。
+// 字符串和数字默认是常量。
+// 但是 array 和 map 不是。他们需要用 "const" 声明为常量。
 var example8A = const ["Example8 const array"],
   example8M = const {"someKey": "Example8 const map"}; 
 example8() {
@@ -119,9 +116,9 @@ example8() {
   print(example8M["someKey"]);
 }
 
-// Loops in Dart take the form of standard for () {} or while () {} loops,
-// slightly more modern for (.. in ..) {}, or functional callbacks with many
-// supported features, starting with forEach.
+// Dart 中的循环使用标准的 for () {} 或 while () {} 的形式，
+// 以及更加现代的 for (.. in ..) {} 的形式, 或者
+// 以 forEach 开头并具有许多特性支持的函数回调的形式。
 var example9A = const ["a", "b"];
 example9() {
   for (var i = 0; i < example9A.length; i++) {
@@ -138,7 +135,7 @@ example9() {
   example9A.forEach((e) => print("Example9 forEach loop '${e}'"));
 }
 
-// To loop over the characters of a string or to extract a substring.
+// 遍历字符串中的每个字符或者提取其子串。
 var example10S = "ab";
 example10() {
   for (var i = 0; i < example10S.length; i++) {
@@ -149,14 +146,14 @@ example10() {
   }
 }
 
-// Int and double are the two supported number formats.
+// 支持两种数字格式 int 和 double 。
 example11() {
   var i = 1 + 320, d = 3.2 + 0.01;
   print("Example11 int ${i}");
   print("Example11 double ${d}");
 }
 
-// DateTime provides date/time arithmetic.
+// DateTime 提供了日期/时间的算法。
 example12() {
   var now = new DateTime.now();
   print("Example12 now '${now}'");
@@ -164,7 +161,7 @@ example12() {
   print("Example12 tomorrow '${now}'");
 }
 
-// Regular expressions are supported.
+// 支持正则表达式。
 example13() {
   var s1 = "some string", s2 = "some", re = new RegExp("^s.+?g\$");
   match(s) {
@@ -178,8 +175,8 @@ example13() {
   match(s2);
 }
 
-// Boolean expressions need to resolve to either true or false, as no
-// implicit conversions are supported.
+// 布尔表达式必需被解析为 true 或 false，
+// 因为不支持隐式转换。
 example14() {
   var v = true;
   if (v) {
@@ -188,17 +185,17 @@ example14() {
   v = null;
   try {
     if (v) {
-      // Never runs
+      // 不会执行
     } else {
-      // Never runs
+      // 不会执行
     }
   } catch (e) {
     print("Example14 null value causes an exception: '${e}'");
   }
 }
 
-// try/catch/finally and throw are used for exception handling.
-// throw takes any object as parameter;
+// try/catch/finally 和 throw 语句用于异常处理。
+// throw 语句可以使用任何对象作为参数。
 example15() {
   try {
     try {
@@ -214,8 +211,8 @@ example15() {
   }
 }
 
-// To be efficient when creating a long string dynamically, use
-// StringBuffer. Or you could join a string array.
+// 要想有效地动态创建长字符串，
+// 应该使用 StringBuffer。 或者 join 一个字符串的数组。
 example16() {
   var sb = new StringBuffer(), a = ["a", "b", "c", "d"], e;
   for (e in a) { sb.write(e); }
@@ -224,8 +221,8 @@ example16() {
   print("Example16 join string array '${a.join()}'");
 }
 
-// Strings can be concatenated by just having string literals next to
-// one another with no further operator needed.
+// 字符串连接只需让相邻的字符串字面量挨着，
+// 不需要额外的操作符。
 example17() {
   print("Example17 "
       "concatenate "
@@ -233,44 +230,41 @@ example17() {
       "just like that");
 }
 
-// Strings have single-quote or double-quote for delimiters with no
-// actual difference between the two. The given flexibility can be good
-// to avoid the need to escape content that matches the delimiter being
-// used. For example, double-quotes of HTML attributes if the string
-// contains HTML content.
+// 字符串使用单引号或双引号做分隔符，二者并没有实际的差异。
+// 这种灵活性可以很好地避免内容中需要转义分隔符的情况。
+// 例如，字符串内容里的 HTML 属性使用了双引号。
 example18() {
   print('Example18 <a href="etc">'
       "Don't can't I'm Etc"
       '</a>');
 }
 
-// Strings with triple single-quotes or triple double-quotes span
-// multiple lines and include line delimiters.
+// 用三个单引号或三个双引号表示的字符串
+// 可以跨越多行，并且包含行分隔符。
 example19() {
   print('''Example19 <a href="etc"> 
 Example19 Don't can't I'm Etc
 Example19 </a>''');
 }
 
-// Strings have the nice interpolation feature with the $ character.
-// With $ { [expression] }, the return of the expression is interpolated.
-// $ followed by a variable name interpolates the content of that variable.
-// $ can be escaped like so \$ to just add it to the string instead.
+// 字符串可以使用 $ 字符插入内容。
+// 使用 $ { [expression] } 的形式，表达式的值会被插入到字符串中。
+// $ 跟着一个变量名会插入变量的值。
+// 如果要在字符串中插入 $ ，可以使用 \$ 的转义形式代替。
 example20() {
   var s1 = "'\${s}'", s2 = "'\$s'";
   print("Example20 \$ interpolation ${s1} or $s2 works.");
 }
 
-// Optional types allow for the annotation of APIs and come to the aid of
-// IDEs so the IDEs can better refactor, auto-complete and check for
-// errors. So far we haven't declared any types and the programs have
-// worked just fine. In fact, types are disregarded during runtime.
-// Types can even be wrong and the program will still be given the
-// benefit of the doubt and be run as though the types didn't matter.
-// There's a runtime parameter that checks for type errors which is
-// the checked mode, which is said to be useful during development time,
-// but which is also slower because of the extra checking and is thus
-// avoided during deployment runtime.
+// 可选类型允许作为 API 的标注，并且可以辅助 IDE，
+// 这样 IDE 可以更好地提供重构、自动完成和错误检测功能。
+// 目前为止我们还没有声明任何类型，并且程序运行地很好。
+// 事实上，类型在运行时会被忽略。
+// 类型甚至可以是错的，并且程序依然可以执行，
+// 好像和类型完全无关一样。
+// 有一个运行时参数可以让程序进入检查模式，它会在运行时检查类型错误。
+// 这在开发时很有用，但是由于增加了额外的检查会使程序变慢，
+// 因此应该避免在部署时使用。
 class Example21 {
   List<String> _names;
   Example21() {
@@ -293,7 +287,7 @@ void example21() {
   print("Example21 names '${o.names}' and length '${o.length}'");
 }
 
-// Class inheritance takes the form of class name extends AnotherClassName {}.
+// 类的继承形式是 class name extends AnotherClassName {} 。
 class Example22A {
   var _name = "Some Name!";
   get name => _name;
@@ -304,13 +298,13 @@ example22() {
   print("Example22 class inheritance '${o.name}'");
 }
 
-// Class mixin is also available, and takes the form of
+// 类也可以使用 mixin 的形式 ：
 // class name extends SomeClass with AnotherClassName {}.
-// It's necessary to extend some class to be able to mixin another one.
-// The template class of mixin cannot at the moment have a constructor.
-// Mixin is mostly used to share methods with distant classes, so the
-// single inheritance doesn't get in the way of reusable code.
-// Mixins follow the "with" statement during the class declaration.
+// 必需继承某个类才能 mixin 另一个类。
+// 当前 mixin 的模板类不能有构造函数。
+// Mixin 主要是用来和辅助的类共享方法的，
+// 这样单一继承就不会影响代码复用。
+// Mixin 声明在类定义的 "with" 关键词后面。
 class Example23A {}
 class Example23Utils {
   addTwo(n1, n2) {
@@ -329,10 +323,9 @@ example23() {
   print("Example23 addTwo(1, 2) results in '${r2}'");
 }
 
-// The Class constructor method uses the same name of the class and
-// takes the form of SomeClass() : super() {}, where the ": super()"
-// part is optional and it's used to delegate constant parameters to the
-// super-parent's constructor.
+// 类的构造函数名和类名相同，形式为
+// SomeClass() : super() {},  其中 ": super()" 的部分是可选的，
+// 它用来传递参数给父类的构造函数。
 class Example24A {
   var _value;
   Example24A({value: "someValue"}) {
@@ -350,9 +343,9 @@ example24() {
   print("Example24 calling super during constructor '${o2.value}'");
 }
 
-// There's a shortcut to set constructor parameters in case of simpler classes.
-// Just use the this.parameterName prefix and it will set the parameter on
-// an instance variable of same name.
+// 对于简单的类，有一种设置构造函数参数的快捷方式。
+// 只需要使用 this.parameterName 的前缀，
+// 它就会把参数设置为同名的实例变量。
 class Example25 {
   var value, anotherValue;
   Example25({this.value, this.anotherValue});
@@ -363,9 +356,9 @@ example25() {
     "'${o.anotherValue}'");
 }
 
-// Named parameters are available when declared between {}.
-// Parameter order can be optional when declared between {}.
-// Parameters can be made optional when declared between [].
+// 可以在大括号 {} 中声明命名参数。
+// 大括号 {} 中声明的参数的顺序是随意的。
+// 在中括号 [] 中声明的参数也是可选的。 
 example26() {
   var _name, _surname, _email;
   setConfig1({name, surname}) {
@@ -385,13 +378,11 @@ example26() {
   "email '${_email}'");
 }
 
-// Variables declared with final can only be set once.
-// In case of classes, final instance variables can be set via constant
-// constructor parameter.
+// 使用 final 声明的变量只能被设置一次。
+// 在类里面，final 实例变量可以通过常量的构造函数参数设置。
 class Example27 {
   final color1, color2;
-  // A little flexibility to set final instance variables with syntax
-  // that follows the :
+  // 更灵活一点的方法是在冒号 : 后面设置 final 实例变量。
   Example27({this.color1, color2}) : color2 = color2;
 }
 example27() {
@@ -400,11 +391,11 @@ example27() {
   print("Example27 color is '${o.color1}' and '${o.color2}'");
 }
 
-// To import a library, use import "libraryPath" or if it's a core library,
-// import "dart:libraryName". There's also the "pub" package management with
-// its own convention of import "package:packageName".
-// See import "dart:collection"; at the top. Imports must come before
-// other code declarations. IterableBase comes from dart:collection.
+// 要导入一个库，使用 import "libraryPath" 的形式，或者如果要导入的是
+// 核心库使用 import "dart:libraryName" 。还有一个称为 "pub" 的包管理工具，
+// 它使用 import "package:packageName" 的约定形式。
+// 看下这个文件顶部的 import "dart:collection"; 语句。 
+// 导入语句必需在其它代码声明之前出现。IterableBase 来自于 dart:collection 。
 class Example28 extends IterableBase {
   var names;
   Example28() {
@@ -417,11 +408,11 @@ example28() {
   o.forEach((name) => print("Example28 '${name}'"));
 }
 
-// For control flow we have:
-// * standard switch with must break statements
-// * if-else if-else and ternary ..?..:.. operator
-// * closures and anonymous functions
-// * break, continue and return statements
+// 对于控制流语句，我们有：
+// * 必需带 break 的标准 switch 语句
+// * if-else 和三元操作符 ..?..:.. 
+// * 闭包和匿名函数
+// * break, continue 和 return 语句
 example29() {
   var v = true ? 30 : 60;
   switch (v) {
@@ -448,12 +439,12 @@ example29() {
     } else {
       continue;
     }
-    // Never gets here.
+    // 不会到这里。
   }
 }
 
-// Parse int, convert double to int, or just keep int when dividing numbers
-// by using the ~/ operation. Let's play a guess game too.
+// 解析 int，把 double 转成 int，或者使用 ~/ 操作符在除法计算时仅保留整数位。
+// 让我们也来场猜数游戏吧。
 example30() {
   var gn, tooHigh = false,
     n, n2 = (2.0).toInt(), top = int.parse("123") ~/ n2, bottom = 0;
@@ -481,11 +472,9 @@ example30() {
   }
 }
 
-// Programs have only one entry point in the main function.
-// Nothing is expected to be executed on the outer scope before a program
-// starts running with what's in its main function.
-// This helps with faster loading and even lazily loading of just what
-// the program needs to startup with.
+// 程序的唯一入口点是 main 函数。
+// 在程序开始执行 main 函数之前，不期望执行任何外层代码。
+// 这样可以帮助程序更快地加载，甚至仅惰性加载程序启动时需要的部分。
 main() {
   print("Learn Dart in 15 minutes!");
   [example1, example2, example3, example4, example5, example6, example7,
@@ -500,8 +489,8 @@ main() {
 
 ## 延伸阅读
 
-Dart 有一个全面的网站。它涵盖了 API 参考、入门向导、文章以及更多，
-包括一个有用的 Dart 在线试用。
+Dart 有一个综合性网站。它涵盖了 API 参考、入门向导、文章以及更多，
+还包括一个有用的在线试用 Dart 页面。
 http://www.dartlang.org/
 http://try.dartlang.org/
 
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