JVM 符号引用和直接引用

public class RefTest {
    
    public void method() {
        int i = 10;
        String str = "test";
    }
}

  Last modified 2020-4-17; size 423 bytes
  MD5 checksum 8b46cded3501cd81c9cef4a1d03dc398
  Compiled from "RefTest.java"
public class com.classloader.RefTest
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Class              #2             // com/classloader/RefTest
   #2 = Utf8               com/classloader/RefTest
   #3 = Class              #4             // java/lang/Object
   #4 = Utf8               java/lang/Object
   #5 = Utf8               <init>
   #6 = Utf8               ()V
   #7 = Utf8               Code
   #8 = Methodref          #3.#9          // java/lang/Object."<init>":()V
   #9 = NameAndType        #5:#6          // "<init>":()V
  #10 = Utf8               LineNumberTable
  #11 = Utf8               LocalVariableTable
  #12 = Utf8               this
  #13 = Utf8               Lcom/classloader/RefTest;
  #14 = Utf8               method
  #15 = String             #16            // test
  #16 = Utf8               test
  #17 = Utf8               i
  #18 = Utf8               I
  #19 = Utf8               str
  #20 = Utf8               Ljava/lang/String;
  #21 = Utf8               SourceFile
  #22 = Utf8               RefTest.java
{
  public com.classloader.RefTest();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #8                  // Method java/lang/Object."<init>":()V
         4: return
      LineNumberTable:
        line 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Lcom/classloader/RefTest;

  public void method();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=3, args_size=1
         0: bipush        10
         2: istore_1
         3: ldc           #15                 // String test
         5: astore_2
         6: return
      LineNumberTable:
        line 6: 0
        line 7: 3
        line 8: 6
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       7     0  this   Lcom/classloader/RefTest;
            3       4     1     i   I
            6       1     2   str   Ljava/lang/String;
}
SourceFile: "RefTest.java"