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JVM String Table(串池)
JVM String Table(串池)
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| public class Test {
public static void main(String[] args) {
String s1 = "a";
String s2 = "b";
String s3 = "ab";
String s4 = "ab";
String s1 = "ab";
}
}
~
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| Classfile /Users/baoguo/codes/demo3/Test.class
Last modified Mar 26, 2022; size 312 bytes
MD5 checksum e8470d9add11ace0d11770668a8ef1c2
Compiled from "Test.java"
public class Test
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #6.#15 // java/lang/Object."<init>":()V
#2 = String #16 // a
#3 = String #17 // b
#4 = String #18 // ab
#5 = Class #19 // Test
#6 = Class #20 // java/lang/Object
#7 = Utf8 <init>
#8 = Utf8 ()V
#9 = Utf8 Code
#10 = Utf8 LineNumberTable
#11 = Utf8 main
#12 = Utf8 ([Ljava/lang/String;)V
#13 = Utf8 SourceFile
#14 = Utf8 Test.java
#15 = NameAndType #7:#8 // "<init>":()V
#16 = Utf8 a
#17 = Utf8 b
#18 = Utf8 ab
#19 = Utf8 Test
#20 = Utf8 java/lang/Object
{
public Test();
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 1: 0
public static void main(java.lang.String[]);
descriptor: ([Ljava/lang/String;)V
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=1, locals=6, args_size=1
0: ldc #2 // String a
2: astore_1
3: ldc #3 // String b
5: astore_2
6: ldc #4 // String ab
8: astore_3
9: ldc #4 // String ab
11: astore 4
13: ldc #4 // String ab
15: astore 5
17: return
LineNumberTable:
line 3: 0
line 4: 3
line 5: 6
line 6: 9
line 7: 13
line 8: 17
}
SourceFile: "Test.java"
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| public class Test {
public static void main(String[] args) {
String s1 = "a";
String s2 = "b";
String s3 = "ab";
String s4 = s1 + s2;
}
}
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| Classfile /Users/baoguo/codes/demo3/Test.class
Last modified Mar 26, 2022; size 465 bytes
MD5 checksum 56db323892928fe4228a815d80cc9acc
Compiled from "Test.java"
public class Test
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #10.#19 // java/lang/Object."<init>":()V
#2 = String #20 // a
#3 = String #21 // b
#4 = String #22 // ab
#5 = Class #23 // java/lang/StringBuilder
#6 = Methodref #5.#19 // java/lang/StringBuilder."<init>":()V
#7 = Methodref #5.#24 // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
#8 = Methodref #5.#25 // java/lang/StringBuilder.toString:()Ljava/lang/String;
#9 = Class #26 // Test
#10 = Class #27 // java/lang/Object
#11 = Utf8 <init>
#12 = Utf8 ()V
#13 = Utf8 Code
#14 = Utf8 LineNumberTable
#15 = Utf8 main
#16 = Utf8 ([Ljava/lang/String;)V
#17 = Utf8 SourceFile
#18 = Utf8 Test.java
#19 = NameAndType #11:#12 // "<init>":()V
#20 = Utf8 a
#21 = Utf8 b
#22 = Utf8 ab
#23 = Utf8 java/lang/StringBuilder
#24 = NameAndType #28:#29 // append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
#25 = NameAndType #30:#31 // toString:()Ljava/lang/String;
#26 = Utf8 Test
#27 = Utf8 java/lang/Object
#28 = Utf8 append
#29 = Utf8 (Ljava/lang/String;)Ljava/lang/StringBuilder;
#30 = Utf8 toString
#31 = Utf8 ()Ljava/lang/String;
{
public Test();
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 1: 0
public static void main(java.lang.String[]);
descriptor: ([Ljava/lang/String;)V
flags: ACC_PUBLIC, ACC_STATIC
Code:
stack=2, locals=5, args_size=1
0: ldc #2 // String a
2: astore_1
3: ldc #3 // String b
5: astore_2
6: ldc #4 // String ab
8: astore_3
9: new #5 // class java/lang/StringBuilder
12: dup
13: invokespecial #6 // Method java/lang/StringBuilder."<init>":()V
16: aload_1
17: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
20: aload_2
21: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
24: invokevirtual #8 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
27: astore 4
29: return
LineNumberTable:
line 3: 0
line 4: 3
line 5: 6
line 6: 9
line 7: 29
}
SourceFile: "Test.java"
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声明: 本文采用 BY-NC-SA 授权。转载请注明转自: Ding Bao Guo