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修正"Java 语法糖详解"中的错别字 #2713

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45 changes: 23 additions & 22 deletions docs/java/basis/syntactic-sugar.md
View file Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -246,7 +246,7 @@ public static transient void print(String strs[])
}
```

从反编译后代码可以看出,可变参数在被使用的时候,他首先会创建一个数组,数组的长度就是调用该方法是传递的实参的个数,然后再把参数值全部放到这个数组当中,然后再把这个数组作为参数传递到被调用的方法中。(注:`trasient` 仅在修饰成员变量时有意义,此处 "修饰方法" 是由于在 javassist 中使用相同数值分别表示 `trasient` 以及 `vararg`,见 [此处](https://github.com/jboss-javassist/javassist/blob/7302b8b0a09f04d344a26ebe57f29f3db43f2a3e/src/main/javassist/bytecode/AccessFlag.java#L32)。)
从反编译后代码可以看出,可变参数在被使用的时候,他首先会创建一个数组,数组的长度就是调用该方法是传递的实参的个数,然后再把参数值全部放到这个数组当中,然后再把这个数组作为参数传递到被调用的方法中。(注:`transient` 仅在修饰成员变量时有意义,此处 "修饰方法" 是由于在 javassist 中使用相同数值分别表示 `transient` 以及 `vararg`,见 [此处](https://github.com/jboss-javassist/javassist/blob/7302b8b0a09f04d344a26ebe57f29f3db43f2a3e/src/main/javassist/bytecode/AccessFlag.java#L32)。)

### 枚举

Expand All @@ -263,7 +263,8 @@ public enum t {
然后我们使用反编译,看看这段代码到底是怎么实现的,反编译后代码内容如下:

```java
public final class T extends Enum
//Java编译器会自动将枚举名处理为合法类名(首字母大写): t -> T
public final class T extends Enum
{
private T(String s, int i)
{
Expand Down Expand Up @@ -308,7 +309,7 @@ public final class T extends Enum
**内部类之所以也是语法糖,是因为它仅仅是一个编译时的概念,`outer.java`里面定义了一个内部类`inner`,一旦编译成功,就会生成两个完全不同的`.class`文件了,分别是`outer.class`和`outer$inner.class`。所以内部类的名字完全可以和它的外部类名字相同。**

```java
public class OutterClass {
public class OuterClass {
private String userName;

public String getUserName() {
Expand Down Expand Up @@ -337,10 +338,10 @@ public class OutterClass {
}
```

以上代码编译后会生成两个 class 文件:`OutterClass$InnerClass.class`、`OutterClass.class` 。当我们尝试对`OutterClass.class`文件进行反编译的时候,命令行会打印以下内容:`Parsing OutterClass.class...Parsing inner class OutterClass$InnerClass.class... Generating OutterClass.jad` 。他会把两个文件全部进行反编译,然后一起生成一个`OutterClass.jad`文件。文件内容如下:
以上代码编译后会生成两个 class 文件:`OuterClass$InnerClass.class`、`OuterClass.class` 。当我们尝试对`OuterClass.class`文件进行反编译的时候,命令行会打印以下内容:`Parsing OuterClass.class...Parsing inner class OuterClass$InnerClass.class... Generating OuterClass.jad` 。他会把两个文件全部进行反编译,然后一起生成一个`OuterClass.jad`文件。文件内容如下:

```java
public class OutterClass
public class OuterClass
{
class InnerClass
{
Expand All @@ -353,16 +354,16 @@ public class OutterClass
this.name = name;
}
private String name;
final OutterClass this0ドル;
final OuterClass this0ドル;

InnerClass()
{
this.this0ドル = OutterClass.this;
this.this0ドル = OuterClass.this;
super();
}
}

public OutterClass()
public OuterClass()
{
}
public String getUserName()
Expand All @@ -385,37 +386,37 @@ public class OutterClass

```java
//省略其他属性
public class OutterClass {
public class OuterClass {
private String userName;
......
class InnerClass{
......
public void printOut(){
System.out.println("Username from OutterClass:"+userName);
System.out.println("Username from OuterClass:"+userName);
}
}
}

// 此时,使用javap -p命令对OutterClass反编译结果:
public classOutterClass {
// 此时,使用javap -p命令对OuterClass反编译结果:
public classOuterClass {
private String userName;
......
static String access000ドル(OutterClass);
static String access000ドル(OuterClass);
}
// 此时,InnerClass的反编译结果:
class OutterClass$InnerClass {
final OutterClass this0ドル;
class OuterClass$InnerClass {
final OuterClass this0ドル;
......
public void printOut();
}

```

实际上,在编译完成之后,inner 实例内部会有指向 outer 实例的引用`this0ドル`,但是简单的`outer.name`是无法访问 private 属性的。从反编译的结果可以看到,outer 中会有一个桥方法`static String access000ドル(OutterClass)`,恰好返回 String 类型,即 userName 属性。正是通过这个方法实现内部类访问外部类私有属性。所以反编译后的`printOut()`方法大致如下:
实际上,在编译完成之后,inner 实例内部会有指向 outer 实例的引用`this0ドル`,但是简单的`outer.name`是无法访问 private 属性的。从反编译的结果可以看到,outer 中会有一个桥方法`static String access000ドル(OuterClass)`,恰好返回 String 类型,即 userName 属性。正是通过这个方法实现内部类访问外部类私有属性。所以反编译后的`printOut()`方法大致如下:

```java
public void printOut() {
System.out.println("Username from OutterClass:" + OutterClass.access000ドル(this.this0ドル));
System.out.println("Username from OuterClass:" + OuterClass.access000ドル(this.this0ドル));
}
```

Expand All @@ -426,7 +427,7 @@ public void printOut() {
3. 匿名内部类、局部内部类通过复制使用局部变量,该变量初始化之后就不能被修改。以下是一个案例:

```java
public class OutterClass {
public class OuterClass {
private String userName;

public void test(){
Expand All @@ -447,10 +448,10 @@ public class OutterClass {
```java
//javap命令反编译Inner的结果
//i被复制进内部类,且为final
class OutterClass1ドルInner {
class OuterClass1ドルInner {
final int val$i;
final OutterClass this0ドル;
OutterClass1ドルInner();
final OuterClass this0ドル;
OuterClass1ドルInner();
public void printName();
}

Expand Down Expand Up @@ -701,7 +702,7 @@ public static transient void main(String args[])
}
else
br.close();
break MISSING_BLOCK_LABEL_113;
break MISSING_BLOCK_LABEL_113; //该标签为反编译工具的生成错误,(不是Java语法本身的内容)属于反编译工具的临时占位符。正常情况下编译器生成的字节码不会包含这种无效标签。
Exception exception;
exception;
if(br != null)
Expand Down

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