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在JAVA的类格式中,字段无标志意味着什么?_Java_Javap - Fatal编程技术网

在JAVA的类格式中,字段无标志意味着什么?

在JAVA的类格式中,字段无标志意味着什么?,java,javap,Java,Javap,以下是我的代码片段: public class Test { public static void main(String[] args) { class EnglishHelloThere { int a=10; } } } 我创建了一个本地类,以查看当没有从编译器为本地类中的变量编写任何修饰符时,我会得到什么样的访问修饰符 这就是我在JAVAP中得到的 Compiled from "Test.java"

以下是我的代码片段:

public class Test {

    public static void main(String[] args) {

        class EnglishHelloThere {
              int a=10;
        }
    }

}
我创建了一个本地类,以查看当没有从编译器为本地类中的变量编写任何修饰符时,我会得到什么样的访问修饰符

这就是我在JAVAP中得到的

  Compiled from "Test.java"
class com.Test$1EnglishHelloThere
  SourceFile: "Test.java"
  EnclosingMethod: #21.#23                // com.Test.main
  InnerClasses:
       #27= #1; //EnglishHelloThere=class com/Test$1EnglishHelloThere
  minor version: 0
  major version: 51
  flags: ACC_SUPER
Constant pool:
   #1 = Class              #2             //  com/Test$1EnglishHelloThere
   #2 = Utf8               com/Test$1EnglishHelloThere
   #3 = Class              #4             //  java/lang/Object
   #4 = Utf8               java/lang/Object
   #5 = Utf8               a
   #6 = Utf8               I
   #7 = Utf8               <init>
   #8 = Utf8               ()V
   #9 = Utf8               Code
  #10 = Methodref          #3.#11         //  java/lang/Object."<init>":()V
  #11 = NameAndType        #7:#8          //  "<init>":()V
  #12 = Fieldref           #1.#13         //  com/Test$1EnglishHelloThere.a:I
  #13 = NameAndType        #5:#6          //  a:I
  #14 = Utf8               LineNumberTable
  #15 = Utf8               LocalVariableTable
  #16 = Utf8               this
  #17 = Utf8               Lcom/Test$1EnglishHelloThere;
  #18 = Utf8               SourceFile
  #19 = Utf8               Test.java
  #20 = Utf8               EnclosingMethod
  #21 = Class              #22            //  com/Test
  #22 = Utf8               com/Test
  #23 = NameAndType        #24:#25        //  main:([Ljava/lang/String;)V
  #24 = Utf8               main
  #25 = Utf8               ([Ljava/lang/String;)V
  #26 = Utf8               InnerClasses
  #27 = Utf8               EnglishHelloThere
{
  int a;
    flags:

  com.Test$1EnglishHelloThere();
    flags:
    Code:
      stack=2, locals=1, args_size=1
         0: aload_0
         1: invokespecial #10                 // Method java/lang/Object."<init>
":()V
         4: aload_0
         5: bipush        10
         7: putfield      #12                 // Field a:I
        10: return
      LineNumberTable:
        line 12: 0
        line 13: 4
        line 12: 10
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0      11     0  this   Lcom/Test$1EnglishHelloThere;
}


那么,默认情况下,访问修饰符是什么类型的呢?

当没有修饰符时,默认值是包私有的(也称为包本地的)。它将可见性限制在同一包内。这与定义类的位置无关(顶级、内部、匿名或本地方法)


也就是说,方法局部类字段的可见性不是很相关,因为它们仅限于方法的范围。

如果没有使用任何其他修饰符指定,它将获得默认/package private修饰符。此外,局部变量不能使用任何其他修饰符(受保护的、公共的或私有的)但为默认值。也可以将其与final一起添加以限制其值更改。有关更多信息,下表显示了每个修饰符允许的成员访问权限

但是这个访问修饰符可能会混淆“注意这里允许的术语” 局部内部类是代码块的局部类 从这里我想说 局部内部类也称为方法局部内部类不是代码所属的类的成员,而是它们所属的代码块的局部成员,就像局部变量一样

无法在定义它们的块之外访问它

例如,假设我在一个包中读写这段代码

package packageone.com;
public class HavingLocalClass {
    public HavingLocalClass() {
        // TODO Auto-generated constructor stub
    }
     void TestMethod(int a){
        class LocalClass{
            int localVar;
            public void display(){
            System.out.println(localVar);
            }

            public LocalClass(int localVar) {
                this.localVar=localVar;
                // TODO Auto-generated constructor stub
            }



            }

            LocalClass lc=new LocalClass(a);
            System.out.println(lc.localVar);
            /* If i directly try to print localVar here it will
                give me error */
            //System.out.println(localVar);//cannot be resolved into variable


    }
}
现在,在同一个包中,如果我尝试打印,我只能通过该方法访问它

package packageone.com;

public class TestingMain {
public static void main(String...strings){
HavingLocalClass tsp= new HavingLocalClass();
tsp.TestMethod(85);
}
}

输出
85

它的可能副本默认情况下不获取访问修饰符,请注意,您不能向局部变量添加
private
protected
。您只能将其设置为
final
@PeterLawrey问题是关于方法本地类中的字段。也就是说,方法局部类字段的可见性不是很相关,因为它们仅限于方法的范围。
package packageone.com;
public class HavingLocalClass {
    public HavingLocalClass() {
        // TODO Auto-generated constructor stub
    }
     void TestMethod(int a){
        class LocalClass{
            int localVar;
            public void display(){
            System.out.println(localVar);
            }

            public LocalClass(int localVar) {
                this.localVar=localVar;
                // TODO Auto-generated constructor stub
            }



            }

            LocalClass lc=new LocalClass(a);
            System.out.println(lc.localVar);
            /* If i directly try to print localVar here it will
                give me error */
            //System.out.println(localVar);//cannot be resolved into variable


    }
}
package packageone.com;

public class TestingMain {
public static void main(String...strings){
HavingLocalClass tsp= new HavingLocalClass();
tsp.TestMethod(85);
}
}