小菜鸟

java菜鸟号正在起航

0%

javap命令

发表于 更新于 分类于 阅读次数： Valine：
本文字数： 9.5k 阅读时长 ≈ 9 分钟

javap命令

1
2
#javap的语法
javap [选项] class文件
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
#javap 的命令选项
  -version                 版本信息
  -v  -verbose             输出附加信息，不包括私有信息，可以与-p结合，查看最全的信息
  -l                       输出行号和局部变量表
  -public                  仅显示公共类和成员
  -protected               显示受保护的/公共类和成员
  -package                 显示程序包/受保护的/公共类
                           和成员 (默认)
  -p  -private             显示所有类和成员
  -c                       对代码进行反汇编
  -s                       输出内部类型签名
  -sysinfo                 显示正在处理的类的系统信息 (路径, 大小, 日期, MD5 散列)
  -constants               显示最终常量
  -classpath <path>        指定查找用户类文件的位置
  -cp <path>               指定查找用户类文件的位置
  -bootclasspath <path>    覆盖引导类文件的位置

我就随便找一个class文件来进行演示一下

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
public class TestString {
    public static void main(String[] args) {
//        String ss = "zxc";
        String s = new String("zxc");
        System.out.println(2 << 3);

        String s1 = "aa";
        String s2 = "bb";
        String s3 = "aabb";
        String s4 = s1+s2;
        String s5 = "aa"+"bb";
        String s6 = s4.intern();
        System.out.println(s3 == s4);// false
        System.out.println(s3 == s5);// true
        System.out.println(s3 == s6);// true
        System.out.println(s4 == s5);// false
        System.out.println(s4 == s6);// false
        System.out.println(s5 == s6);// true

    }
}

使用命令javap -v TestString.class

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
  Last modified 2022-1-9; size 1454 bytes
  MD5 checksum 618e1797fdaef66f8ebe9aab023dedc6
  Compiled from "TestString.java"
public class com.zhanghe.study.string.TestString
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool: #常量池
   #1 = Methodref          #17.#43        // java/lang/Object."<init>":()V
   #2 = Class              #44            // java/lang/String
   #3 = String             #45            // zxc
   #4 = Methodref          #2.#46         // java/lang/String."<init>":(Ljava/lang/String;)V
   #5 = Fieldref           #47.#48        // java/lang/System.out:Ljava/io/PrintStream;
   #6 = Methodref          #49.#50        // java/io/PrintStream.println:(I)V
   #7 = String             #51            // aa
   #8 = String             #52            // bb
   #9 = String             #53            // aabb
  #10 = Class              #54            // java/lang/StringBuilder
  #11 = Methodref          #10.#43        // java/lang/StringBuilder."<init>":()V
  #12 = Methodref          #10.#55        // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #13 = Methodref          #10.#56        // java/lang/StringBuilder.toString:()Ljava/lang/String;
  #14 = Methodref          #2.#57         // java/lang/String.intern:()Ljava/lang/String;
  #15 = Methodref          #49.#58        // java/io/PrintStream.println:(Z)V
  #16 = Class              #59            // com/zhanghe/study/string/TestString
  #17 = Class              #60            // java/lang/Object
  #18 = Utf8               <init>
  #19 = Utf8               ()V
  #20 = Utf8               Code
  #21 = Utf8               LineNumberTable
  #22 = Utf8               LocalVariableTable
  #23 = Utf8               this
  #24 = Utf8               Lcom/zhanghe/study/string/TestString;
  #25 = Utf8               main
  #26 = Utf8               ([Ljava/lang/String;)V
  #27 = Utf8               args
  #28 = Utf8               [Ljava/lang/String;
  #29 = Utf8               s
  #30 = Utf8               Ljava/lang/String;
  #31 = Utf8               s1
  #32 = Utf8               s2
  #33 = Utf8               s3
  #34 = Utf8               s4
  #35 = Utf8               s5
  #36 = Utf8               s6
  #37 = Utf8               StackMapTable
  #38 = Class              #28            // "[Ljava/lang/String;"
  #39 = Class              #44            // java/lang/String
  #40 = Class              #61            // java/io/PrintStream
  #41 = Utf8               SourceFile
  #42 = Utf8               TestString.java
  #43 = NameAndType        #18:#19        // "<init>":()V
  #44 = Utf8               java/lang/String
  #45 = Utf8               zxc
  #46 = NameAndType        #18:#62        // "<init>":(Ljava/lang/String;)V
  #47 = Class              #63            // java/lang/System
  #48 = NameAndType        #64:#65        // out:Ljava/io/PrintStream;
  #49 = Class              #61            // java/io/PrintStream
  #50 = NameAndType        #66:#67        // println:(I)V
  #51 = Utf8               aa
  #52 = Utf8               bb
  #53 = Utf8               aabb
  #54 = Utf8               java/lang/StringBuilder
  #55 = NameAndType        #68:#69        // append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #56 = NameAndType        #70:#71        // toString:()Ljava/lang/String;
  #57 = NameAndType        #72:#71        // intern:()Ljava/lang/String;
  #58 = NameAndType        #66:#73        // println:(Z)V
  #59 = Utf8               com/zhanghe/study/string/TestString
  #60 = Utf8               java/lang/Object
  #61 = Utf8               java/io/PrintStream
  #62 = Utf8               (Ljava/lang/String;)V
  #63 = Utf8               java/lang/System
  #64 = Utf8               out
  #65 = Utf8               Ljava/io/PrintStream;
  #66 = Utf8               println
  #67 = Utf8               (I)V
  #68 = Utf8               append
  #69 = Utf8               (Ljava/lang/String;)Ljava/lang/StringBuilder;
  #70 = Utf8               toString
  #71 = Utf8               ()Ljava/lang/String;
  #72 = Utf8               intern
  #73 = Utf8               (Z)V
{
  public com.zhanghe.study.string.TestString();
    descriptor: ()V
    flags: 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 7: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Lcom/zhanghe/study/string/TestString;

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=3, locals=8, args_size=1
         0: new           #2                  // class java/lang/String
         3: dup
         4: ldc           #3                  // String zxc
         6: invokespecial #4                  // Method java/lang/String."<init>":(Ljava/lang/String;)V
         9: astore_1
        10: getstatic     #5                  // Field java/lang/System.out:Ljava/io/PrintStream;
        13: bipush        16
        15: invokevirtual #6                  // Method java/io/PrintStream.println:(I)V
        18: ldc           #7                  // String aa
        20: astore_2
        21: ldc           #8                  // String bb
        23: astore_3
        24: ldc           #9                  // String aabb
        26: astore        4
        28: new           #10                 // class java/lang/StringBuilder
        31: dup
        32: invokespecial #11                 // Method java/lang/StringBuilder."<init>":()V
        35: aload_2
        36: invokevirtual #12                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
        39: aload_3
        40: invokevirtual #12                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
        43: invokevirtual #13                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
        46: astore        5
        48: ldc           #9                  // String aabb
        50: astore        6
        52: aload         5
        54: invokevirtual #14                 // Method java/lang/String.intern:()Ljava/lang/String;
        57: astore        7
        59: getstatic     #5                  // Field java/lang/System.out:Ljava/io/PrintStream;
        62: aload         4
        64: aload         5
        66: if_acmpne     73
        69: iconst_1
        70: goto          74
        73: iconst_0
        74: invokevirtual #15                 // Method java/io/PrintStream.println:(Z)V
        77: getstatic     #5                  // Field java/lang/System.out:Ljava/io/PrintStream;
        80: aload         4
        82: aload         6
        84: if_acmpne     91
        87: iconst_1
        88: goto          92
        91: iconst_0
        92: invokevirtual #15                 // Method java/io/PrintStream.println:(Z)V
        95: getstatic     #5                  // Field java/lang/System.out:Ljava/io/PrintStream;
        98: aload         4
       100: aload         7
       102: if_acmpne     109
       105: iconst_1
       106: goto          110
       109: iconst_0
       110: invokevirtual #15                 // Method java/io/PrintStream.println:(Z)V
       113: getstatic     #5                  // Field java/lang/System.out:Ljava/io/PrintStream;
       116: aload         5
       118: aload         6
       120: if_acmpne     127
       123: iconst_1
       124: goto          128
       127: iconst_0
       128: invokevirtual #15                 // Method java/io/PrintStream.println:(Z)V
       131: getstatic     #5                  // Field java/lang/System.out:Ljava/io/PrintStream;
       134: aload         5
       136: aload         7
       138: if_acmpne     145
       141: iconst_1
       142: goto          146
       145: iconst_0
       146: invokevirtual #15                 // Method java/io/PrintStream.println:(Z)V
       149: getstatic     #5                  // Field java/lang/System.out:Ljava/io/PrintStream;
       152: aload         6
       154: aload         7
       156: if_acmpne     163
       159: iconst_1
       160: goto          164
       163: iconst_0
       164: invokevirtual #15                 // Method java/io/PrintStream.println:(Z)V
       167: return
      LineNumberTable:
        line 10: 0
        line 11: 10
        line 13: 18
        line 14: 21
        line 15: 24
        line 16: 28
        line 17: 48
        line 18: 52
        line 19: 59
        line 20: 77
        line 21: 95
        line 22: 113
        line 23: 131
        line 24: 149
        line 26: 167
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0     168     0  args   [Ljava/lang/String;
           10     158     1     s   Ljava/lang/String;
           21     147     2    s1   Ljava/lang/String;
           24     144     3    s2   Ljava/lang/String;
           28     140     4    s3   Ljava/lang/String;
           48     120     5    s4   Ljava/lang/String;
           52     116     6    s5   Ljava/lang/String;
           59     109     7    s6   Ljava/lang/String;
      StackMapTable: number_of_entries = 12
        frame_type = 255 /* full_frame */
          offset_delta = 73
          locals = [ class "[Ljava/lang/String;", class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String ]
          stack = [ class java/io/PrintStream ]
        frame_type = 255 /* full_frame */
          offset_delta = 0
          locals = [ class "[Ljava/lang/String;", class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String ]
          stack = [ class java/io/PrintStream, int ]
        frame_type = 80 /* same_locals_1_stack_item */
          stack = [ class java/io/PrintStream ]
        frame_type = 255 /* full_frame */
          offset_delta = 0
          locals = [ class "[Ljava/lang/String;", class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String ]
          stack = [ class java/io/PrintStream, int ]
        frame_type = 80 /* same_locals_1_stack_item */
          stack = [ class java/io/PrintStream ]
        frame_type = 255 /* full_frame */
          offset_delta = 0
          locals = [ class "[Ljava/lang/String;", class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String ]
          stack = [ class java/io/PrintStream, int ]
        frame_type = 80 /* same_locals_1_stack_item */
          stack = [ class java/io/PrintStream ]
        frame_type = 255 /* full_frame */
          offset_delta = 0
          locals = [ class "[Ljava/lang/String;", class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String ]
          stack = [ class java/io/PrintStream, int ]
        frame_type = 80 /* same_locals_1_stack_item */
          stack = [ class java/io/PrintStream ]
        frame_type = 255 /* full_frame */
          offset_delta = 0
          locals = [ class "[Ljava/lang/String;", class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String ]
          stack = [ class java/io/PrintStream, int ]
        frame_type = 80 /* same_locals_1_stack_item */
          stack = [ class java/io/PrintStream ]
        frame_type = 255 /* full_frame */
          offset_delta = 0
          locals = [ class "[Ljava/lang/String;", class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String, class java/lang/String ]
          stack = [ class java/io/PrintStream, int ]
}
SourceFile: "TestString.java"

相关文章

欢迎关注我的其它发布渠道