🏷 Strings
9 patterns
Topic: Strings
All Java patterns related to Strings — java.evolved
Language
Text blocks for multiline strings
Old
String json = "{\n" +
" \"name\": \"Duke\",\n" +
" \"age\": 30\n" +
"}";
Modern
String json = """
{
"name": "Duke",
"age": 30
}""";
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JDK 15+
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Strings
String.isBlank()
Old
boolean blank =
str.trim().isEmpty();
// or: str.trim().length() == 0
Modern
boolean blank = str.isBlank();
// handles Unicode whitespace too
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JDK 11+
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Strings
String.strip() vs trim()
Old
// trim() only removes ASCII whitespace
// (chars <= U+0020)
String clean = str.trim();
Modern
// strip() removes all Unicode whitespace
String clean = str.strip();
String left = str.stripLeading();
String right = str.stripTrailing();
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JDK 11+
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Strings
String.repeat()
Old
StringBuilder sb = new StringBuilder();
for (int i = 0; i < 3; i++) {
sb.append("abc");
}
String result = sb.toString();
Modern
String result = "abc".repeat(3);
// "abcabcabc"
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JDK 11+
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Strings
String.indent() and transform()
Old
String[] lines = text.split("\n");
StringBuilder sb = new StringBuilder();
for (String line : lines) {
sb.append(" ").append(line)
.append("\n");
}
String indented = sb.toString();
Modern
String indented = text.indent(4);
String result = text
.transform(String::strip)
.transform(s -> s.replace(" ", "-"));
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JDK 12+
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Strings
String.formatted()
Old
String msg = String.format(
"Hello %s, you are %d",
name, age
);
Modern
String msg =
"Hello %s, you are %d"
.formatted(name, age);
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JDK 15+
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Strings
String chars as stream
Old
for (int i = 0; i < str.length(); i++) {
char c = str.charAt(i);
if (Character.isDigit(c)) {
process(c);
}
}
Modern
str.chars()
.filter(Character::isDigit)
.forEach(c -> process((char) c));
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JDK 9+
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Strings
String.lines() for line splitting
Old
String text = "one\ntwo\nthree";
String[] lines = text.split("\n");
for (String line : lines) {
System.out.println(line);
}
Modern
String text = "one\ntwo\nthree";
text.lines().forEach(IO::println);
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JDK 11+
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Date/Time
HexFormat
Old
// Pad to 2 digits, uppercase
String hex = String.format(
"%02X", byteValue);
// Parse hex string
int val = Integer.parseInt(
"FF", 16);
Modern
var hex = HexFormat.of()
.withUpperCase();
String s = hex.toHexDigits(
byteValue);
byte[] bytes =
hex.parseHex("48656C6C6F");
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JDK 17+
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