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companion object和object 从kotlin转java分析

article 2025/3/21 6:39:45

说明

companion object 中
companion类中的方法是普通的方法
在外部类中生成静态变量，静态companion 对象

object MyClass2 中
类中方法是普通方法
在MyClass2中生成静态变量，静态MyClass2对象，

一 companion object 使用 kotlin转java


package test.e

class Test1 {


}

fun main() {
//    MyClass.MyClass2.printHello()
    MyClass.printHello()

}
class MyClass {

    var a  =10

   companion  object  {

        var b =1
//        @JvmStatic
        fun printHello() {
            println("Hello, World!")
        }
    }
}


 调用方法
//MyClass.printHello()


------------------------------------------
// Test1.java
package test.e;

import kotlin.Metadata;

@Metadata(
   mv = {2, 0, 0},
   k = 1,
   xi = 48,
   d1 = {"\u0000\f\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0002\b\u0002\u0018\u00002\u00020\u0001B\u0005¢\u0006\u0002\u0010\u0002¨\u0006\u0003"},
   d2 = {"Ltest/e/Test1;", "", "()V", "untitled"}
)
public final class Test1 {
}
// MyClass.java
package test.e;

import kotlin.Metadata;
import kotlin.jvm.internal.DefaultConstructorMarker;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {2, 0, 0},
   k = 1,
   xi = 48,
   d1 = {"\u0000\u0014\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0002\b\u0002\n\u0002\u0010\b\n\u0002\b\u0006\u0018\u0000 \t2\u00020\u0001:\u0001\tB\u0005¢\u0006\u0002\u0010\u0002R\u001a\u0010\u0003\u001a\u00020\u0004X\u0086\u000e¢\u0006\u000e\n\u0000\u001a\u0004\b\u0005\u0010\u0006\"\u0004\b\u0007\u0010\b¨\u0006\n"},
   d2 = {"Ltest/e/MyClass;", "", "()V", "a", "", "getA", "()I", "setA", "(I)V", "Companion", "untitled"}
)
public final class MyClass {
   @NotNull
   **public static final Companion Companion = new Companion((DefaultConstructorMarker)null);**
   private int a = 10;
   private static int b = 1;

   public final int getA() {
      return this.a;
   }

   public final void setA(int var1) {
      this.a = var1;
   }

   @Metadata(
      mv = {2, 0, 0},
      k = 1,
      xi = 48,
      d1 = {"\u0000\u001a\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0002\b\u0002\n\u0002\u0010\b\n\u0002\b\u0005\n\u0002\u0010\u0002\n\u0000\b\u0086\u0003\u0018\u00002\u00020\u0001B\u0007\b\u0002¢\u0006\u0002\u0010\u0002J\u0006\u0010\t\u001a\u00020\nR\u001a\u0010\u0003\u001a\u00020\u0004X\u0086\u000e¢\u0006\u000e\n\u0000\u001a\u0004\b\u0005\u0010\u0006\"\u0004\b\u0007\u0010\b¨\u0006\u000b"},
      d2 = {"Ltest/e/MyClass$Companion;", "", "()V", "b", "", "getB", "()I", "setB", "(I)V", "printHello", "", "untitled"}
   )
   public static final class Companion {
      private Companion() {
      }

      public final int getB() {
         return MyClass.b;
      }

      public final void setB(int var1) {
         MyClass.b = var1;
      }

      public final void printHello() {
         String var1 = "Hello, World!";
         System.out.println(var1);
      }

      // $FF: synthetic method
      public Companion(DefaultConstructorMarker $constructor_marker) {
         this();
      }
   }
}
// Test1Kt.java
package test.e;

import kotlin.Metadata;

@Metadata(
   mv = {2, 0, 0},
   k = 2,
   xi = 48,
   d1 = {"\u0000\b\n\u0000\n\u0002\u0010\u0002\n\u0000\u001a\u0006\u0010\u0000\u001a\u00020\u0001¨\u0006\u0002"},
   d2 = {"main", "", "untitled"}
)
public final class Test1Kt {
   public static final void main() {
      MyClass.Companion.printHello();
   }

   // $FF: synthetic method
   public static void main(String[] args) {
      main();
   }
}

二 object kotlin转java

package test.e

class Test1 {

}

fun main() {
    MyClass.MyClass2.printHello()
//    MyClass.printHello()

}
class MyClass {

    var a  =10

     object MyClass2 {
        var b =1
//        @JvmStatic
        fun printHello() {
            println("Hello, World!")
        }
    }
}


 调用方法
//MyClass.printHello()

------------------------------
// Test1.java
package test.e;

import kotlin.Metadata;

@Metadata(
   mv = {2, 0, 0},
   k = 1,
   xi = 48,
   d1 = {"\u0000\f\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0002\b\u0002\u0018\u00002\u00020\u0001B\u0005¢\u0006\u0002\u0010\u0002¨\u0006\u0003"},
   d2 = {"Ltest/e/Test1;", "", "()V", "untitled"}
)
public final class Test1 {
}
// MyClass.java
package test.e;

import kotlin.Metadata;
import org.jetbrains.annotations.NotNull;

@Metadata(
   mv = {2, 0, 0},
   k = 1,
   xi = 48,
   d1 = {"\u0000\u0014\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0002\b\u0002\n\u0002\u0010\b\n\u0002\b\u0006\u0018\u00002\u00020\u0001:\u0001\tB\u0005¢\u0006\u0002\u0010\u0002R\u001a\u0010\u0003\u001a\u00020\u0004X\u0086\u000e¢\u0006\u000e\n\u0000\u001a\u0004\b\u0005\u0010\u0006\"\u0004\b\u0007\u0010\b¨\u0006\n"},
   d2 = {"Ltest/e/MyClass;", "", "()V", "a", "", "getA", "()I", "setA", "(I)V", "MyClass2", "untitled"}
)
public final class MyClass {
   private int a = 10;

   public final int getA() {
      return this.a;
   }

   public final void setA(int var1) {
      this.a = var1;
   }

   @Metadata(
      mv = {2, 0, 0},
      k = 1,
      xi = 48,
      d1 = {"\u0000\u001a\n\u0002\u0018\u0002\n\u0002\u0010\u0000\n\u0002\b\u0002\n\u0002\u0010\b\n\u0002\b\u0005\n\u0002\u0010\u0002\n\u0000\bÆ\u0002\u0018\u00002\u00020\u0001B\u0007\b\u0002¢\u0006\u0002\u0010\u0002J\u0006\u0010\t\u001a\u00020\nR\u001a\u0010\u0003\u001a\u00020\u0004X\u0086\u000e¢\u0006\u000e\n\u0000\u001a\u0004\b\u0005\u0010\u0006\"\u0004\b\u0007\u0010\b¨\u0006\u000b"},
      d2 = {"Ltest/e/MyClass$MyClass2;", "", "()V", "b", "", "getB", "()I", "setB", "(I)V", "printHello", "", "untitled"}
   )
   public static final class MyClass2 {
      @NotNull
      **public static final MyClass2 INSTANCE = new MyClass2();**
      private static int b = 1;

      private MyClass2() {
      }

      public final int getB() {
         return b;
      }

      public final void setB(int var1) {
         b = var1;
      }

      public final void printHello() {
         String var1 = "Hello, World!";
         System.out.println(var1);
      }
   }
}
// Test1Kt.java
package test.e;

import kotlin.Metadata;

@Metadata(
   mv = {2, 0, 0},
   k = 2,
   xi = 48,
   d1 = {"\u0000\b\n\u0000\n\u0002\u0010\u0002\n\u0000\u001a\u0006\u0010\u0000\u001a\u00020\u0001¨\u0006\u0002"},
   d2 = {"main", "", "untitled"}
)
public final class Test1Kt {
   public static final void main() {
      MyClass.MyClass2.INSTANCE.printHello();
   }

   // $FF: synthetic method
   public static void main(String[] args) {
      main();
   }
}

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