源代码
package org.example;
public class Main {
public static void main(String[] args) {
int a = 1;
while (a < 10) {
a++;
if (a < 5) {
System.out.println("a<5");
} else {
System.out.println("a>=5");
}
}
}
}
语法树
<?xml version='1.0' encoding='UTF-8' ?>
<CompilationUnit Image='' PackageName='org.example' declarationsAreInDefaultPackage='false'>
<PackageDeclaration Image='' Name='org.example' PackageNameImage='org.example'>
<Name Image='org.example' />
</PackageDeclaration>
<TypeDeclaration Image=''>
<ClassOrInterfaceDeclaration Abstract='false' BinaryName='org.example.Main' Default='false' Final='false' Image='Main' Interface='false' Local='false' Modifiers='1' Native='false' Nested='false' NonSealed='false' PackagePrivate='false' Private='false' Protected='false' Public='true' Sealed='false' SimpleName='Main' Static='false' Strictfp='false' Synchronized='false' Transient='false' TypeKind='CLASS' Volatile='false'>
<ClassOrInterfaceBody AnonymousInnerClass='false' EnumChild='false' Image=''>
<ClassOrInterfaceBodyDeclaration AnonymousInnerClass='false' EnumChild='false' Image='' Kind='METHOD'>
<MethodDeclaration Abstract='false' Arity='1' Default='false' Final='false' Image='' InterfaceMember='false' Kind='METHOD' MethodName='main' Modifiers='17' Name='main' Native='false' PackagePrivate='false' Private='false' Protected='false' Public='true' Static='true' Strictfp='false' Synchronized='false' SyntacticallyAbstract='false' SyntacticallyPublic='true' Transient='false' Void='true' Volatile='false'>
<ResultType Image='' Void='true' returnsArray='false' />
<MethodDeclarator Image='main' ParameterCount='1'>
<FormalParameters Image='' ParameterCount='1' Size='1'>
<FormalParameter Abstract='false' Array='true' ArrayDepth='1' Default='false' ExplicitReceiverParameter='false' Final='false' Image='' Modifiers='0' Native='false' PackagePrivate='true' Private='false' Protected='false' Public='false' Static='false' Strictfp='false' Synchronized='false' Transient='false' TypeInferred='false' Varargs='false' Volatile='false'>
<Type Array='true' ArrayDepth='1' ArrayType='true' Image='' TypeImage='String'>
<ReferenceType Array='true' ArrayDepth='1' Image=''>
<ClassOrInterfaceType AnonymousClass='false' Array='true' ArrayDepth='1' Image='String' ReferenceToClassSameCompilationUnit='false' />
</ReferenceType>
</Type>
<VariableDeclaratorId Array='false' ArrayDepth='0' ArrayType='true' ExceptionBlockParameter='false' ExplicitReceiverParameter='false' Field='false' Final='false' ForeachVariable='false' FormalParameter='true' Image='args' LambdaParameter='false' LocalVariable='false' Name='args' PatternBinding='false' ResourceDeclaration='false' TypeInferred='false' VariableName='args' />
</FormalParameter>
</FormalParameters>
</MethodDeclarator>
<Block Image='' containsComment='false'>
<BlockStatement Allocation='false' Image=''>
<LocalVariableDeclaration Abstract='false' Array='false' ArrayDepth='0' Default='false' Final='false' Image='' Modifiers='0' Native='false' PackagePrivate='true' Private='false' Protected='false' Public='false' Static='false' Strictfp='false' Synchronized='false' Transient='false' TypeInferred='false' VariableName='a' Volatile='false'>
<Type Array='false' ArrayDepth='0' ArrayType='false' Image='' TypeImage='int'>
<PrimitiveType Array='false' ArrayDepth='0' Boolean='false' Image='int' />
</Type>
<VariableDeclarator Image='' Initializer='true' Name='a'>
<VariableDeclaratorId Array='false' ArrayDepth='0' ArrayType='false' ExceptionBlockParameter='false' ExplicitReceiverParameter='false' Field='false' Final='false' ForeachVariable='false' FormalParameter='false' Image='a' LambdaParameter='false' LocalVariable='true' Name='a' PatternBinding='false' ResourceDeclaration='false' TypeInferred='false' VariableName='a' />
<VariableInitializer Image=''>
<Expression Image='' StandAlonePrimitive='true'>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Literal CharLiteral='false' DoubleLiteral='false' EscapedStringLiteral='1' FloatLiteral='false' Image='1' IntLiteral='true' LongLiteral='false' SingleCharacterStringLiteral='false' StringLiteral='false' TextBlock='false' TextBlockContent='1' ValueAsDouble='NaN' ValueAsFloat='NaN' ValueAsInt='1' ValueAsLong='1' />
</PrimaryPrefix>
</PrimaryExpression>
</Expression>
</VariableInitializer>
</VariableDeclarator>
</LocalVariableDeclaration>
</BlockStatement>
<BlockStatement Allocation='false' Image=''>
<Statement Image=''>
<WhileStatement Image=''>
<Expression Image='' StandAlonePrimitive='false'>
<RelationalExpression Image='&lt;'>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Name Image='a' />
</PrimaryPrefix>
</PrimaryExpression>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Literal CharLiteral='false' DoubleLiteral='false' EscapedStringLiteral='10' FloatLiteral='false' Image='10' IntLiteral='true' LongLiteral='false' SingleCharacterStringLiteral='false' StringLiteral='false' TextBlock='false' TextBlockContent='10' ValueAsDouble='NaN' ValueAsFloat='NaN' ValueAsInt='10' ValueAsLong='10' />
</PrimaryPrefix>
</PrimaryExpression>
</RelationalExpression>
</Expression>
<Statement Image=''>
<Block Image='' containsComment='false'>
<BlockStatement Allocation='false' Image=''>
<Statement Image=''>
<StatementExpression Image=''>
<PostfixExpression Image='++' Operator='++'>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Name Image='a' />
</PrimaryPrefix>
</PrimaryExpression>
</PostfixExpression>
</StatementExpression>
</Statement>
</BlockStatement>
<BlockStatement Allocation='false' Image=''>
<Statement Image=''>
<IfStatement Else='true' Image=''>
<Expression Image='' StandAlonePrimitive='false'>
<RelationalExpression Image='&lt;'>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Name Image='a' />
</PrimaryPrefix>
</PrimaryExpression>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Literal CharLiteral='false' DoubleLiteral='false' EscapedStringLiteral='5' FloatLiteral='false' Image='5' IntLiteral='true' LongLiteral='false' SingleCharacterStringLiteral='false' StringLiteral='false' TextBlock='false' TextBlockContent='5' ValueAsDouble='NaN' ValueAsFloat='NaN' ValueAsInt='5' ValueAsLong='5' />
</PrimaryPrefix>
</PrimaryExpression>
</RelationalExpression>
</Expression>
<Statement Image=''>
<Block Image='' containsComment='false'>
<BlockStatement Allocation='false' Image=''>
<Statement Image=''>
<StatementExpression Image=''>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Name Image='System.out.println' />
</PrimaryPrefix>
<PrimarySuffix ArgumentCount='1' Arguments='true' ArrayDereference='false' Image=''>
<Arguments ArgumentCount='1' Image='' Size='1'>
<ArgumentList Image='' Size='1'>
<Expression Image='' StandAlonePrimitive='false'>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Literal CharLiteral='false' DoubleLiteral='false' EscapedStringLiteral='"a&lt;5"' FloatLiteral='false' Image='"a&lt;5"' IntLiteral='false' LongLiteral='false' SingleCharacterStringLiteral='false' StringLiteral='true' TextBlock='false' TextBlockContent='"a&lt;5"' ValueAsDouble='NaN' ValueAsFloat='NaN' ValueAsInt='0' ValueAsLong='0' />
</PrimaryPrefix>
</PrimaryExpression>
</Expression>
</ArgumentList>
</Arguments>
</PrimarySuffix>
</PrimaryExpression>
</StatementExpression>
</Statement>
</BlockStatement>
</Block>
</Statement>
<Statement Image=''>
<Block Image='' containsComment='false'>
<BlockStatement Allocation='false' Image=''>
<Statement Image=''>
<StatementExpression Image=''>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Name Image='System.out.println' />
</PrimaryPrefix>
<PrimarySuffix ArgumentCount='1' Arguments='true' ArrayDereference='false' Image=''>
<Arguments ArgumentCount='1' Image='' Size='1'>
<ArgumentList Image='' Size='1'>
<Expression Image='' StandAlonePrimitive='false'>
<PrimaryExpression Image=''>
<PrimaryPrefix Image='' SuperModifier='false' ThisModifier='false'>
<Literal CharLiteral='false' DoubleLiteral='false' EscapedStringLiteral='"a>=5"' FloatLiteral='false' Image='"a>=5"' IntLiteral='false' LongLiteral='false' SingleCharacterStringLiteral='false' StringLiteral='true' TextBlock='false' TextBlockContent='"a>=5"' ValueAsDouble='NaN' ValueAsFloat='NaN' ValueAsInt='0' ValueAsLong='0' />
</PrimaryPrefix>
</PrimaryExpression>
</Expression>
</ArgumentList>
</Arguments>
</PrimarySuffix>
</PrimaryExpression>
</StatementExpression>
</Statement>
</BlockStatement>
</Block>
</Statement>
</IfStatement>
</Statement>
</BlockStatement>
</Block>
</Statement>
</WhileStatement>
</Statement>
</BlockStatement>
</Block>
</MethodDeclaration>
</ClassOrInterfaceBodyDeclaration>
</ClassOrInterfaceBody>
</ClassOrInterfaceDeclaration>
</TypeDeclaration>
</CompilationUnit>
编译
mvn clean compile
或者javac
class反编译字节码
(base) hogwarts: example seveniruby$ javap -v -l -s -c Main.class
Classfile /Users/seveniruby/ke/shift_left/java_demo2/target/classes/org/example/Main.class
Last modified 2023年8月17日; size 639 bytes
MD5 checksum 99b52f268dd2e7ecefc4d4131b8a77b0
Compiled from "Main.java"
public class org.example.Main
minor version: 0
major version: 55
flags: (0x0021) ACC_PUBLIC, ACC_SUPER
this_class: #6 // org/example/Main
super_class: #7 // java/lang/Object
interfaces: 0, fields: 0, methods: 2, attributes: 1
Constant pool:
#1 = Methodref #7.#24 // java/lang/Object."<init>":()V
#2 = Fieldref #25.#26 // java/lang/System.out:Ljava/io/PrintStream;
#3 = String #27 // a<5
#4 = Methodref #28.#29 // java/io/PrintStream.println:(Ljava/lang/String;)V
#5 = String #30 // a>=5
#6 = Class #31 // org/example/Main
#7 = Class #32 // java/lang/Object
#8 = Utf8 <init>
#9 = Utf8 ()V
#10 = Utf8 Code
#11 = Utf8 LineNumberTable
#12 = Utf8 LocalVariableTable
#13 = Utf8 this
#14 = Utf8 Lorg/example/Main;
#15 = Utf8 main
#16 = Utf8 ([Ljava/lang/String;)V
#17 = Utf8 args
#18 = Utf8 [Ljava/lang/String;
#19 = Utf8 a
#20 = Utf8 I
#21 = Utf8 StackMapTable
#22 = Utf8 SourceFile
#23 = Utf8 Main.java
#24 = NameAndType #8:#9 // "<init>":()V
#25 = Class #33 // java/lang/System
#26 = NameAndType #34:#35 // out:Ljava/io/PrintStream;
#27 = Utf8 a<5
#28 = Class #36 // java/io/PrintStream
#29 = NameAndType #37:#38 // println:(Ljava/lang/String;)V
#30 = Utf8 a>=5
#31 = Utf8 org/example/Main
#32 = Utf8 java/lang/Object
#33 = Utf8 java/lang/System
#34 = Utf8 out
#35 = Utf8 Ljava/io/PrintStream;
#36 = Utf8 java/io/PrintStream
#37 = Utf8 println
#38 = Utf8 (Ljava/lang/String;)V
{
public org.example.Main();
descriptor: ()V
flags: (0x0001) ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: return
LineNumberTable:
line 3: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this Lorg/example/Main;
public static void main(java.lang.String[]);
descriptor: ([Ljava/lang/String;)V
flags: (0x0009) ACC_PUBLIC, ACC_STATIC
Code:
stack=2, locals=2, args_size=1
0: iconst_1
1: istore_1
2: iload_1
3: bipush 10
5: if_icmpge 38
8: iinc 1, 1
11: iload_1
12: iconst_5
13: if_icmpge 27
16: getstatic #2 // Field java/lang/System.out:Ljava/io/PrintStream;
19: ldc #3 // String a<5
21: invokevirtual #4 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
24: goto 2
27: getstatic #2 // Field java/lang/System.out:Ljava/io/PrintStream;
30: ldc #5 // String a>=5
32: invokevirtual #4 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
35: goto 2
38: return
LineNumberTable:
line 5: 0
line 6: 2
line 7: 8
line 8: 11
line 9: 16
line 11: 27
line 14: 38
LocalVariableTable:
Start Length Slot Name Signature
0 39 0 args [Ljava/lang/String;
2 37 1 a I
StackMapTable: number_of_entries = 3
frame_type = 252 /* append */
offset_delta = 2
locals = [ int ]
frame_type = 24 /* same */
frame_type = 10 /* same */
}
SourceFile: "Main.java"
jvm指令集
https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-6.html
UnsupportedClassVersionError
错误: 加载主类 org.sonarsource.scanner.cli.Main 时出现 LinkageError
java.lang.UnsupportedClassVersionError: org/sonarsource/scanner/cli/Main has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0
Class File Versions
| JDK Version | Bytecode Version |
|---|---|
| Java 1.0 | 45.0 |
| Java 1.1 | 45.3 |
| Java 1.2 | 46.0 |
| Java 1.3 | 47.0 |
| Java 1.4 | 48.0 |
| Java 5 | 49.0 |
| Java 6 | 50.0 |
| Java 7 | 51.0 |
| Java 8 | 52.0 |
| Java 9 | 53.0 |
| Java 10 | 54.0 |
| Java 11 | 55.0 |
| Java 12 | 56.0 |
| Java 13 | 57.0 |
| Java 14 | 58.0 |
| Java 15 | 59.0 |
| Java 16 | 60.0 |
| Java 17 | 61.0 |
| Java 18 | 62.0 |
| Java 19 | 63.0 |
| Java 20 | 64.0 |
| Java 21 | 65.0 |
| Java 22 | 66.0 |