JVM synchronized关键字所生成的字节码
一、创建测试类
package com.example.jvm.bytecode;
public class MyTest2 {
String str = "Welcome";
private int x = 5;
public static Integer in = 10;
public static void main(String[] args) {
MyTest2 myTest2 = new MyTest2();
myTest2.setX(8);
in = 20;
}
public void setX(int x){
this.x = x;
}
}
反编译MyTest2.class文件
D:\workspace\study\ jvm_demo\build\classes\java\main\com\example\jvm\bytecode>javap -verbose MyTest2.class
Classfile /D:/workspace/study/ jvm_demo/build/classes/java/main/com/example/jvm/bytecode/MyTest2.class
Last modified 2019-6-26; size 847 bytes
MD5 checksum d8f82e3e7255d9a738591c52d3a5417b
Compiled from "MyTest2.java"
public class com.example.jvm.bytecode.MyTest2
SourceFile: "MyTest2.java"
minor version: 0
major version: 51
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #10.#34 // java/lang/Object."<init>":()V
#2 = String #35 // Welcome
#3 = Fieldref #5.#36 // com/example/jvm/bytecode/MyTest2.str:Ljava/lang/String;
#4 = Fieldref #5.#37 // com/example/jvm/bytecode/MyTest2.x:I
#5 = Class #38 // com/example/jvm/bytecode/MyTest2
#6 = Methodref #5.#34 // com/example/jvm/bytecode/MyTest2."<init>":()V
#7 = Methodref #5.#39 // com/example/jvm/bytecode/MyTest2.setX:(I)V
#8 = Methodref #40.#41 // java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
#9 = Fieldref #5.#42 // com/example/jvm/bytecode/MyTest2.in:Ljava/lang/Integer;
#10 = Class #43 // java/lang/Object
#11 = Utf8 str
#12 = Utf8 Ljava/lang/String;
#13 = Utf8 x
#14 = Utf8 I
#15 = Utf8 in
#16 = Utf8 Ljava/lang/Integer;
#17 = Utf8 <init>
#18 = Utf8 ()V
#19 = Utf8 Code
#20 = Utf8 LineNumberTable
#21 = Utf8 LocalVariableTable
#22 = Utf8 this
#23 = Utf8 Lcom/example/jvm/bytecode/MyTest2;
#24 = Utf8 main
#25 = Utf8 ([Ljava/lang/String;)V
#26 = Utf8 args
#27 = Utf8 [Ljava/lang/String;
#28 = Utf8 myTest2
#29 = Utf8 setX
#30 = Utf8 (I)V
#31 = Utf8 <clinit>
#32 = Utf8 SourceFile
#33 = Utf8 MyTest2.java
#34 = NameAndType #17:#18 // "<init>":()V
#35 = Utf8 Welcome
#36 = NameAndType #11:#12 // str:Ljava/lang/String;
#37 = NameAndType #13:#14 // x:I
#38 = Utf8 com/example/jvm/bytecode/MyTest2
#39 = NameAndType #29:#30 // setX:(I)V
#40 = Class #44 // java/lang/Integer
#41 = NameAndType #45:#46 // valueOf:(I)Ljava/lang/Integer;
#42 = NameAndType #15:#16 // in:Ljava/lang/Integer;
#43 = Utf8 java/lang/Object
#44 = Utf8 java/lang/Integer
#45 = Utf8 valueOf
#46 = Utf8 (I)Ljava/lang/Integer;
{
java.lang.String str;
flags: public static java.lang.Integer in;
flags: ACC_PUBLIC, ACC_STATIC public com.example.jvm.bytecode.MyTest2();
flags: ACC_PUBLIC
Code:
stack=2, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: aload_0
5: ldc #2 // String Welcome
7: putfield #3 // Field str:Ljava/lang/String;
10: aload_0
11: iconst_5
12: putfield #4 // Field x:I
15: return
LineNumberTable:
line 3: 0
line 5: 4
line 7: 10
LocalVariableTable:
Start Length Slot Name Signature
0 16 0 this Lcom/example/jvm/bytecode/MyTest2; public static void main(java.lang.String[]);
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=2, locals=2, args_size=1
0: new #5 // class com/example/jvm/bytecode/MyTest2
3: dup
4: invokespecial #6 // Method "<init>":()V
7: astore_1
8: aload_1
9: bipush 8
11: invokevirtual #7 // Method setX:(I)V
14: bipush 20
16: invokestatic #8 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
19: putstatic #9 // Field in:Ljava/lang/Integer;
22: return
LineNumberTable:
line 12: 0
line 14: 8
line 16: 14
line 17: 22
LocalVariableTable:
Start Length Slot Name Signature
0 23 0 args [Ljava/lang/String;
8 15 1 myTest2 Lcom/example/jvm/bytecode/MyTest2; public void setX(int);
flags: ACC_PUBLIC
Code:
stack=2, locals=2, args_size=2
0: aload_0
1: iload_1
2: putfield #4 // Field x:I
5: return
LineNumberTable:
line 20: 0
line 21: 5
LocalVariableTable:
Start Length Slot Name Signature
0 6 0 this Lcom/example/jvm/bytecode/MyTest2;
0 6 1 x I static {};
flags: ACC_STATIC
Code:
stack=1, locals=0, args_size=0
0: bipush 10
2: invokestatic #8 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
5: putstatic #9 // Field in:Ljava/lang/Integer;
8: return
LineNumberTable:
line 9: 0
}
二、将setX改为private
此时需要使用javap -verbose -p MyTest2.class才能显示私有方法
D:\workspace\study\ jvm_demo\build\classes\java\main\com\example\jvm\bytecode>javap -verbose -p MyTest2.class
Classfile /D:/workspace/study/ jvm_demo/build/classes/java/main/com/example/jvm/bytecode/MyTest2.class
Last modified 2019-6-27; size 847 bytes
MD5 checksum f9ed848bb768588b932c395b40c509a8
Compiled from "MyTest2.java"
public class com.example.jvm.bytecode.MyTest2
SourceFile: "MyTest2.java"
minor version: 0
major version: 51
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #10.#34 // java/lang/Object."<init>":()V
#2 = String #35 // Welcome
#3 = Fieldref #5.#36 // com/example/jvm/bytecode/MyTest2.str:Ljava/lang/String;
#4 = Fieldref #5.#37 // com/example/jvm/bytecode/MyTest2.x:I
#5 = Class #38 // com/example/jvm/bytecode/MyTest2
#6 = Methodref #5.#34 // com/example/jvm/bytecode/MyTest2."<init>":()V
#7 = Methodref #5.#39 // com/example/jvm/bytecode/MyTest2.setX:(I)V
#8 = Methodref #40.#41 // java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
#9 = Fieldref #5.#42 // com/example/jvm/bytecode/MyTest2.in:Ljava/lang/Integer;
#10 = Class #43 // java/lang/Object
#11 = Utf8 str
#12 = Utf8 Ljava/lang/String;
#13 = Utf8 x
#14 = Utf8 I
#15 = Utf8 in
#16 = Utf8 Ljava/lang/Integer;
#17 = Utf8 <init>
#18 = Utf8 ()V
#19 = Utf8 Code
#20 = Utf8 LineNumberTable
#21 = Utf8 LocalVariableTable
#22 = Utf8 this
#23 = Utf8 Lcom/example/jvm/bytecode/MyTest2;
#24 = Utf8 main
#25 = Utf8 ([Ljava/lang/String;)V
#26 = Utf8 args
#27 = Utf8 [Ljava/lang/String;
#28 = Utf8 myTest2
#29 = Utf8 setX
#30 = Utf8 (I)V
#31 = Utf8 <clinit>
#32 = Utf8 SourceFile
#33 = Utf8 MyTest2.java
#34 = NameAndType #17:#18 // "<init>":()V
#35 = Utf8 Welcome
#36 = NameAndType #11:#12 // str:Ljava/lang/String;
#37 = NameAndType #13:#14 // x:I
#38 = Utf8 com/example/jvm/bytecode/MyTest2
#39 = NameAndType #29:#30 // setX:(I)V
#40 = Class #44 // java/lang/Integer
#41 = NameAndType #45:#46 // valueOf:(I)Ljava/lang/Integer;
#42 = NameAndType #15:#16 // in:Ljava/lang/Integer;
#43 = Utf8 java/lang/Object
#44 = Utf8 java/lang/Integer
#45 = Utf8 valueOf
#46 = Utf8 (I)Ljava/lang/Integer;
{
java.lang.String str;
flags: private int x;
flags: ACC_PRIVATE public static java.lang.Integer in;
flags: ACC_PUBLIC, ACC_STATIC public com.example.jvm.bytecode.MyTest2();
flags: ACC_PUBLIC
Code:
stack=2, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: aload_0
5: ldc #2 // String Welcome
7: putfield #3 // Field str:Ljava/lang/String;
10: aload_0
11: iconst_5
12: putfield #4 // Field x:I
15: return
LineNumberTable:
line 3: 0
line 5: 4
line 7: 10
LocalVariableTable:
Start Length Slot Name Signature
0 16 0 this Lcom/example/jvm/bytecode/MyTest2; public static void main(java.lang.String[]);
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=2, locals=2, args_size=1
0: new #5 // class com/example/jvm/bytecode/MyTest2
3: dup
4: invokespecial #6 // Method "<init>":()V
7: astore_1
8: aload_1
9: bipush 8
11: invokespecial #7 // Method setX:(I)V
14: bipush 20
16: invokestatic #8 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
19: putstatic #9 // Field in:Ljava/lang/Integer;
22: return
LineNumberTable:
line 12: 0
line 14: 8
line 16: 14
line 17: 22
LocalVariableTable:
Start Length Slot Name Signature
0 23 0 args [Ljava/lang/String;
8 15 1 myTest2 Lcom/example/jvm/bytecode/MyTest2; private void setX(int);
flags: ACC_PRIVATE
Code:
stack=2, locals=2, args_size=2
0: aload_0
1: iload_1
2: putfield #4 // Field x:I
5: return
LineNumberTable:
line 20: 0
line 21: 5
LocalVariableTable:
Start Length Slot Name Signature
0 6 0 this Lcom/example/jvm/bytecode/MyTest2;
0 6 1 x I static {};
flags: ACC_STATIC
Code:
stack=1, locals=0, args_size=0
0: bipush 10
2: invokestatic #8 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
5: putstatic #9 // Field in:Ljava/lang/Integer;
8: return
LineNumberTable:
line 9: 0
}
三、现在将setX方法增加synchronized 修饰符
private synchronized void setX(int x)
反编译后无synchronized和有synchronized的区别如下图：
四、在类中增加test方法，方法里面使用了synchronize
private void test(String str){
synchronized (obj){
System.out.println("hello world");
}
}
反编译后如下：
private void test(java.lang.String);
flags: ACC_PRIVATE
Code:
stack=2, locals=4, args_size=2
0: aload_0
1: getfield #6 // Field obj:Ljava/lang/Object;
4: dup
5: astore_2
6: monitorenter
7: getstatic #12 // Field java/lang/System.out:Ljava/io/PrintStream;
10: ldc #13 // String hello world
12: invokevirtual #14 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
15: aload_2
16: monitorexit
17: goto 25
20: astore_3
21: aload_2
22: monitorexit
23: aload_3
24: athrow
25: return
Exception table:
from to target type
7 17 20 any
20 23 20 any
LineNumberTable:
line 26: 0
line 27: 7
line 28: 15
line 29: 25
LocalVariableTable:
Start Length Slot Name Signature
0 26 0 this Lcom/example/jvm/bytecode/MyTest2;
0 26 1 str Ljava/lang/String;
StackMapTable: number_of_entries = 2
frame_type = 255 /* full_frame */
offset_delta = 20
locals = [ class com/example/jvm/bytecode/MyTest2, class java/lang/String, class java/lang/Object ]
stack = [ class java/lang/Throwable ]
frame_type = 250 /* chop */
offset_delta = 4
出现了6: monitorenter和22: monitorexit
给当前MyTest2类所对应的class对象上锁
private synchronized static void test2(){
}
给当前对象上锁
private synchronized void setX(int x){
this.x = x;
}
五、字节码文件分析
最终需要分析的java文件
package com.example.jvm.bytecode;
public class MyTest2 {
String str = "Welcome";
private int x = 5;
public static Integer in = 10;
public static void main(String[] args) {
MyTest2 myTest2 = new MyTest2();
myTest2.setX(8);
in = 20;
}
private synchronized void setX(int x){
this.x = x;
}
private void test(String str){
synchronized (str){
System.out.println("hello world");
}
}
private synchronized static void test2(){
}
}
然后反编译MyTest2.class
Classfile /D:/workspace/study/ jvm_demo/build/classes/java/main/com/example/jvm/bytecode/MyTest2.class
Last modified 2019-6-27; size 1265 bytes
MD5 checksum 1ca3fedabb74af431cc850f3f87b7763
Compiled from "MyTest2.java"
public class com.example.jvm.bytecode.MyTest2
SourceFile: "MyTest2.java"
minor version: 0
major version: 51
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #13.#45 // java/lang/Object."<init>":()V
#2 = String #46 // Welcome
#3 = Fieldref #5.#47 // com/example/jvm/bytecode/MyTest2.str:Ljava/lang/String;
#4 = Fieldref #5.#48 // com/example/jvm/bytecode/MyTest2.x:I
#5 = Class #49 // com/example/jvm/bytecode/MyTest2
#6 = Methodref #5.#45 // com/example/jvm/bytecode/MyTest2."<init>":()V
#7 = Methodref #5.#50 // com/example/jvm/bytecode/MyTest2.setX:(I)V
#8 = Methodref #51.#52 // java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
#9 = Fieldref #5.#53 // com/example/jvm/bytecode/MyTest2.in:Ljava/lang/Integer;
#10 = Fieldref #54.#55 // java/lang/System.out:Ljava/io/PrintStream;
#11 = String #56 // hello world
#12 = Methodref #57.#58 // java/io/PrintStream.println:(Ljava/lang/String;)V
#13 = Class #59 // java/lang/Object
#14 = Utf8 str
#15 = Utf8 Ljava/lang/String;
#16 = Utf8 x
#17 = Utf8 I
#18 = Utf8 in
#19 = Utf8 Ljava/lang/Integer;
#20 = Utf8 <init>
#21 = Utf8 ()V
#22 = Utf8 Code
#23 = Utf8 LineNumberTable
#24 = Utf8 LocalVariableTable
#25 = Utf8 this
#26 = Utf8 Lcom/example/jvm/bytecode/MyTest2;
#27 = Utf8 main
#28 = Utf8 ([Ljava/lang/String;)V
#29 = Utf8 args
#30 = Utf8 [Ljava/lang/String;
#31 = Utf8 myTest2
#32 = Utf8 setX
#33 = Utf8 (I)V
#34 = Utf8 test
#35 = Utf8 (Ljava/lang/String;)V
#36 = Utf8 StackMapTable
#37 = Class #49 // com/example/jvm/bytecode/MyTest2
#38 = Class #60 // java/lang/String
#39 = Class #59 // java/lang/Object
#40 = Class #61 // java/lang/Throwable
#41 = Utf8 test2
#42 = Utf8 <clinit>
#43 = Utf8 SourceFile
#44 = Utf8 MyTest2.java
#45 = NameAndType #20:#21 // "<init>":()V
#46 = Utf8 Welcome
#47 = NameAndType #14:#15 // str:Ljava/lang/String;
#48 = NameAndType #16:#17 // x:I
#49 = Utf8 com/example/jvm/bytecode/MyTest2
#50 = NameAndType #32:#33 // setX:(I)V
#51 = Class #62 // java/lang/Integer
#52 = NameAndType #63:#64 // valueOf:(I)Ljava/lang/Integer;
#53 = NameAndType #18:#19 // in:Ljava/lang/Integer;
#54 = Class #65 // java/lang/System
#55 = NameAndType #66:#67 // out:Ljava/io/PrintStream;
#56 = Utf8 hello world
#57 = Class #68 // java/io/PrintStream
#58 = NameAndType #69:#35 // println:(Ljava/lang/String;)V
#59 = Utf8 java/lang/Object
#60 = Utf8 java/lang/String
#61 = Utf8 java/lang/Throwable
#62 = Utf8 java/lang/Integer
#63 = Utf8 valueOf
#64 = Utf8 (I)Ljava/lang/Integer;
#65 = Utf8 java/lang/System
#66 = Utf8 out
#67 = Utf8 Ljava/io/PrintStream;
#68 = Utf8 java/io/PrintStream
#69 = Utf8 println
{
java.lang.String str;
flags: private int x;
flags: ACC_PRIVATE public static java.lang.Integer in;
flags: ACC_PUBLIC, ACC_STATIC public com.example.jvm.bytecode.MyTest2();
flags: ACC_PUBLIC
Code:
stack=2, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."<init>":()V
4: aload_0
5: ldc #2 // String Welcome
7: putfield #3 // Field str:Ljava/lang/String;
10: aload_0
11: iconst_5
12: putfield #4 // Field x:I
15: return
LineNumberTable:
line 3: 0
line 5: 4
line 7: 10
LocalVariableTable:
Start Length Slot Name Signature
0 16 0 this Lcom/example/jvm/bytecode/MyTest2; public static void main(java.lang.String[]);
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=2, locals=2, args_size=1
0: new #5 // class com/example/jvm/bytecode/MyTest2
3: dup
4: invokespecial #6 // Method "<init>":()V
7: astore_1
8: aload_1
9: bipush 8
11: invokespecial #7 // Method setX:(I)V
14: bipush 20
16: invokestatic #8 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
19: putstatic #9 // Field in:Ljava/lang/Integer;
22: return
LineNumberTable:
line 12: 0
line 14: 8
line 16: 14
line 17: 22
LocalVariableTable:
Start Length Slot Name Signature
0 23 0 args [Ljava/lang/String;
8 15 1 myTest2 Lcom/example/jvm/bytecode/MyTest2; private synchronized void setX(int);
flags: ACC_PRIVATE, ACC_SYNCHRONIZED
Code:
stack=2, locals=2, args_size=2
0: aload_0
1: iload_1
2: putfield #4 // Field x:I
5: return
LineNumberTable:
line 20: 0
line 21: 5
LocalVariableTable:
Start Length Slot Name Signature
0 6 0 this Lcom/example/jvm/bytecode/MyTest2;
0 6 1 x I private void test(java.lang.String);
flags: ACC_PRIVATE
Code:
stack=2, locals=4, args_size=2
0: aload_1
1: dup
2: astore_2
3: monitorenter
4: getstatic #10 // Field java/lang/System.out:Ljava/io/PrintStream;
7: ldc #11 // String hello world
9: invokevirtual #12 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
12: aload_2
13: monitorexit
14: goto 22
17: astore_3
18: aload_2
19: monitorexit
20: aload_3
21: athrow
22: return
Exception table:
from to target type
4 14 17 any
17 20 17 any
LineNumberTable:
line 24: 0
line 25: 4
line 26: 12
line 27: 22
LocalVariableTable:
Start Length Slot Name Signature
0 23 0 this Lcom/example/jvm/bytecode/MyTest2;
0 23 1 str Ljava/lang/String;
StackMapTable: number_of_entries = 2
frame_type = 255 /* full_frame */
offset_delta = 17
locals = [ class com/example/jvm/bytecode/MyTest2, class java/lang/String, class java/lang/Object ]
stack = [ class java/lang/Throwable ]
frame_type = 250 /* chop */
offset_delta = 4 private static synchronized void test2();
flags: ACC_PRIVATE, ACC_STATIC, ACC_SYNCHRONIZED
Code:
stack=0, locals=0, args_size=0
0: return
LineNumberTable:
line 31: 0 static {};
flags: ACC_STATIC
Code:
stack=1, locals=0, args_size=0
0: bipush 10
2: invokestatic #8 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
5: putstatic #9 // Field in:Ljava/lang/Integer;
8: return
LineNumberTable:
line 9: 0
}
然后打开WinHex打开MyTest2.class 文件
JVM synchronized关键字所生成的字节码的更多相关文章
- synchronized关键字所生成的字节码详细分析
在之前已经将如下这样的源文件对应的字节码文件完整的分析完了,如下: 这次再来写一个内容稍丰富一点的类,准备再来从头至尾的来分析一下,对其字节码的理解进一步巩固,如下: 然后用javap -verbos ...
- eclipse中的项目无法在build/classes目录下生成.class字节码
转载 原文链接:https://www.cnblogs.com/iceblow/p/6648715.html 1.首先确定project->Build Automatically是否勾选上: ...
- 【synchronized锁】通过synchronized锁 反编译查看字节码指令分析synchronized关键字修饰方法与代码块的区别
前提: 首先要铺垫几个前置的知识: Java中的锁如sychronize锁是对象锁,Java对象头中具有标识位,当对象锁升级为重量级锁时,重量级锁的标识位会指向监视器monitor, 而每个Java对 ...
- 【JVM】模板解释器--如何根据字节码生成汇编码？
1.背景 仅针对JVM的模板解释器: 如何根据opcode和寻址模式,将bytecode生成汇编码. 本文的示例中所使用的字节码和汇编码,请参见上篇博文:按值传递还是按引用? 2.寻址模式 本文不打算 ...
- JVM（三）类加载与字节码技术
1.类文件结构 首先获得.class字节码文件 方法: 在文本文档里写入java代码(文件名与类名一致),将文件类型改为.java 在文件对应目录下运行cmd,执行javac XXX.java 以下是 ...
- 深入了解java虚拟机（JVM） 第十三章 虚拟机字节码执行引擎
一.概述 执行引擎是java虚拟机最核心的组成部件之一.虚拟机的执行引擎由自己实现,所以可以自行定制指令集与执行引擎的结构体系,并且能够执行那些不被硬件直接支持的指令集格式.所有的Java虚拟机的执行 ...
- java动态代理——jvm指令集基本概念和方法字节码结构的进一步探究及proxy源码分析四
前文地址 https://www.cnblogs.com/tera/p/13336627.html 本系列文章主要是博主在学习spring aop的过程中了解到其使用了java动态代理,本着究根问底的 ...
- javap生成的字节码
https://www.zhihu.com/question/49470442/answer/135812845http://blog.csdn.net/tzs_1041218129
- JVM 字节码（四）静态方法、构造代码、this 以及 synchronized 关键字
JVM 字节码(四)静态方法.构造代码.this 以及 synchronized 关键字 一.静态代码 public class ByteCodeStatic { private static fin ...
随机推荐
- 用PL/SQL工具连接Oracle数据库的时报错：ORA-12638: 身份证明检索失败的解决方法
本地客户端用PLSQL Developer连接远程数据库时提示: ORA-12638: 身份证明检索失败!!! 解决方法一: 此目录下F:\myorcl\product\11.2.0\client_1 ...
- layui.table前端+后台处理+分页
前端 注:监听工具条没有详细写,但路子一样的 @section head{ <script src="~/Content/jquery-easyui-1.5.5.4/jquery.ea ...
- Linux中通过ssh将客户端与服务端的远程连接
前提需要:1.在VMware中装上两台linux虚拟机,本博客使用的都是CentOS 7.2.两部虚拟机可以通过命令ping通.3.两部虚拟机中已经通过yum本地仓库安装了sshd服务. 首先 1. ...
- 2013.4.19 - KDD第一天
其实昨天KDD就开始了,不过今天算是我跟KDD的第一天. 昨天夜里就短信跟中秋聊了一会儿,然后中秋说他一天都在弄数据库,连不上怒了.然后我跟他说明天我来.于是今天就在图书馆弄KDD,数据是用数据库 ...
- html相对字体
文章:使用 rem 设置文字大小 使用rem作为字体单位.
- 洛谷 P1280 尼克的任务题解
题目链接:https://www.luogu.org/problem/P1280 题目描述 尼克每天上班之前都连接上英特网,接收他的上司发来的邮件,这些邮件包含了尼克主管的部门当天要完成的全部任务,每 ...
- dt二次开发之-地区链接伪静态标签用法
用法:开启伪静态功能,参照前台,看看哪里有按照地区浏览,然后打开对应的模块和模板,修改 <a href="{$MOD[linkurl]}search.php?areaid={$v[ar ...
- machine learning (6)---how to choose features, polynomial regression
how to choose features, polynomial regression:通过定义更适合我们的feature,选择更好的模型,使我们的曲线与数据更好的拟合(而不仅仅是一条直线) 可以 ...
- 黄杉杉 --java第八次作业
题目:编写一个应用程序,创建一个矩形类,类中具有长.宽两个成员变量和求周长的方法.再创建一个矩形类的子类——正方形类,类中定义求面积方法.重写求周长的方法.在主类中,输入一个正方形边长,创建正方形对象 ...
- 轮播图方法一，把每个slider-item看成一个对象进行轮播
focus-slider 只用于存放轮播图片,方便修改图片内容 其他的按照默认创建即可. 注意这里的slider.html文件是在 text文件下面 index.html <!DOCTYPE ...