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
|
import java.io.File;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import static java.lang.StringTemplate.RAW;
import static java.util.FormatProcessor.FMT;
/**
* Examples taken from <a href="https://openjdk.org/jeps/430">JEP 430</a>
*/
public aspect StringPatternsPreview1Aspect {
public static void main(String[] args) {}
before() : execution(* main(String[])) {
System.out.println(thisJoinPoint);
// Embedded expressions can be strings
String firstName = "Bill", lastName = "Duck";
// TODO: Due to https://github.com/eclipse-jdt/eclipse.jdt.core/issues/1719, this is currently rendered incorrectly
System.out.println(STR."\{firstName} \{lastName}");
// Embedded expressions can perform arithmetic
int x = 10, y = 20;
System.out.println(STR."\{x} + \{y} = \{x + y}");
// Embedded expressions can invoke methods and access fields
System.out.println(STR."You have a \{getOfferType()} waiting for you!");
Request req = new Request();
System.out.println(STR."Access at \{req.date} \{req.time} from \{req.ipAddress}");
// Embedded expressions can use double quotes without escaping them
String filePath = "_dummy.dat";
File file = new File(filePath);
System.out.println(STR."The file \{filePath} \{file.exists() ? "does" : "does not"} exist");
// Embedded expressions can span multiple lines
System.out.println(
STR."The time is \{
DateTimeFormatter
.ofPattern("HH:mm:ss")
.format(LocalTime.of(11, 11, 11))
} or roughly eleven after eleven"
);
// Embedded expressions can be nested
String[] fruit = { "apples", "oranges", "peaches" };
System.out.println(STR."\{fruit[0]}, \{STR."\{fruit[1]}, \{fruit[2]}"}\n");
// Embedded expressions can be used in multi-line strings
String title = "My Web Page";
String text = "Hello, world";
String html = STR."""
<html>
<head>
<title>\{title}</title>
</head>
<body>
<p>\{text}</p>
</body>
</html>
""";
System.out.println(html);
// The FMT template processor interprets format specifiers which appear to the left of embedded expressions.
// The format specifiers are the same as those defined in java.util.Formatter.
Rectangle[] zone = new Rectangle[] {
new Rectangle("Alfa", 17.8, 31.4),
new Rectangle("Bravo", 9.6, 12.4),
new Rectangle("Charlie", 7.1, 11.23),
};
String table = FMT."""
Description Width Height Area
%-12s\{zone[0].name} %7.2f\{zone[0].width} %7.2f\{zone[0].height} %7.2f\{zone[0].area()}
%-12s\{zone[1].name} %7.2f\{zone[1].width} %7.2f\{zone[1].height} %7.2f\{zone[1].area()}
%-12s\{zone[2].name} %7.2f\{zone[2].width} %7.2f\{zone[2].height} %7.2f\{zone[2].area()}
\{" ".repeat(28)} Total %7.2f\{zone[0].area() + zone[1].area() + zone[2].area()}
""";
System.out.println(table);
// Built-in security: Each template expression needs to pass through a processor.
String name = "Joan";
StringTemplate stringTemplate = RAW."My name is \{name}";
String processedTemplate = STR.process(stringTemplate);
System.out.println(processedTemplate);
}
static Object getOfferType() {
return "special New Year's sale discount";
}
static class Request {
LocalDate date;
LocalTime time;
InetAddress ipAddress;
Request() {
LocalDateTime dateTime = LocalDateTime.of(2011, 11, 11, 11, 11, 11);
date = dateTime.toLocalDate();
time = dateTime.toLocalTime();
try {
// localhost/127.0.0.1
ipAddress = InetAddress.getByAddress("localhost", new byte[] { 127, 0, 0, 1 });
} catch (UnknownHostException e) {
throw new RuntimeException(e);
}
}
}
record Rectangle(String name, double width, double height) {
double area() {
return width * height;
}
}
}
|
