String
non-primitive
replaceAll(), replace()
public class Main
{
public static void main(String[] args)
{
String str = "Hello, World_123!!";
str = str.replaceAll("[^\\w+]", "");
System.out.println(str);
}
}
결과 : HelloWorld_123
public class Main
{
public static void main(String[] args)
{
String str = "Hello, World_123!!";
String charsToRemove = ",_!";
for (char c : charsToRemove.toCharArray()) {
str = str.replace(String.valueOf(c), "");
}
System.out.println(str);
}
}
결과 : Hello World123
Ref
toCharArray()
public class Main
{
public static void main(String[] args)
{
String str = "Soobin";
char[] c = new char[str.length()];
for (int i = 0; i < str.length(); i++)
{
c[i] = str.charAt(i);
System.out.println(c[i]);
}
String str2 = "soobin";
char[] arr = str2.toCharArray();
for (char value : arr) {
System.out.println(value);
}
}
}
indexOf(), lastIndexOf()
public class Main
{
public static void main(String[] args)
{
String str = "Sooobin";
int a = str.indexOf("o"); // 1
int b = str.indexOf("o", 2); // 2
int c = str.lastIndexOf("o"); // -1 (no o from index 3
System.out.println(a + " : " + str.charAt(a)); // 1o (index 1 is o
System.out.println(b + " : " + str.charAt(b)); // 2o (index 2 is o
System.out.println(c + " : " + str.charAt(c)); // 3o (index 3 is o
}
}
1 : o
2 : o
3 : o
charAt()
str.charAt(idx);
toUpperCase(), toLowerCase()
public class Main
{
public static void main(String[] args)
{
String str = "SoooBin";
System.out.println(str.toUpperCase());
System.out.println(str.toLowerCase());
}
}
SOOOBIN
sooobin
equals(str2)
str.equals(str2);
compareTo(str2)
str.compareTo(str2);
//returns s1-s2, in dictionary order so a-b returns -1
contains(str2)
str.contains(str2);
length()
str.length();
public class Main
{
public static void main(String[] args)
{
String str = "SoooBin";
String str2 = "SoooBin";
String str3 = new String("SoooBin");
String str4 = "SoooBin22";
System.out.println(str == str2); // true
System.out.println(str == str3); // false
System.out.println(str.equals(str2)); // true
System.out.println(str.equals(str3)); // true
System.out.println(str.compareTo(str2)); // 0
System.out.println(str.compareTo(str4)); // -2
System.out.println(str.contains("oo")); // true
}
}
startsWith("str2"), endWith("str2")
public class Main
{
public static void main(String[] args)
{
String str = "SoooBin";
System.out.println(str.startsWith("S")); // true
System.out.println(str.startsWith("s")); // false
System.out.println(str.endsWith("Bin")); // true
System.out.println(str.endsWith("bin")); // false
}
}
substring(incl,excl)
str.substring(incl,excl)
// incl: inclusive index, included,
// excl: exclusive index, exclude
public class Main
{
public static void main(String[] args)
{
String str = "SooBin Jung";
// substring() 메소드를 사용하여 문자열을 추출
String str1 = str.substring(0, 6);
String str2 = str.substring(6);
System.out.println(str1); // SooBin
System.out.println(str2); // Jung
}
}
split("regrex")
str_array = str.split(“ “);
//return string array separated by spaces.
// “Hello world” returns [“Hello”,”world”]
public class Main
{
public static void main(String[] args)
{
String str = "SooBin Jung";
// split
String[] strArr = str.split(" ");
for (String s : strArr)
{
System.out.println(s);
}
}
}
trim()
public class Main
{
public static void main(String[] args)
{
String str = " SooBin Jung ";
// trim
System.out.println(str.trim()); // "SooBin Jung"
}
}
Ref
StringBuilder
public class StringBuilder_Ex {
public static void main(String[] args) {
String s = "abcdefg";
StringBuilder sb = new StringBuilder(s); // String -> StringBuilder
System.out.println("처음 상태 : " + sb); //처음상태 : abcdefg
System.out.println("문자열 String 변환 : " + sb.toString()); //String 변환하기
System.out.println("문자열 추출 : " + sb.substring(2,4)); //문자열 추출하기
System.out.println("문자열 추가 : " + sb.insert(2,"추가")); //문자열 추가하기
System.out.println("문자열 삭제 : " + sb.delete(2,4)); //문자열 삭제하기
System.out.println("문자열 연결 : " + sb.append("hijk")); //문자열 붙이기
System.out.println("문자열의 길이 : " + sb.length()); //문자열의 길이구하기
System.out.println("용량의 크기 : " + sb.capacity()); //용량의 크기 구하기
System.out.println("문자열 역순 변경 : " + sb.reverse()); //문자열 뒤집기
System.out.println("마지막 상태 : " + sb); //마지막상태 : kjihgfedcba
}
}
StringBuffer
public class StringBuffer_Ex {
public static void main(String[] args) {
String s = "abcdefg";
StringBuffer sb = new StringBuffer(s); // String -> StringBuffer
System.out.println("처음 상태 : " + sb); //처음상태 : abcdefg
System.out.println("문자열 String 변환 : " + sb.toString()); //String 변환하기
System.out.println("문자열 추출 : " + sb.substring(2,4)); //문자열 추출하기
System.out.println("문자열 추가 : " + sb.insert(2,"추가")); //문자열 추가하기
System.out.println("문자열 삭제 : " + sb.delete(2,4)); //문자열 삭제하기
System.out.println("문자열 연결 : " + sb.append("hijk")); //문자열 붙이기
System.out.println("문자열의 길이 : " + sb.length()); //문자열의 길이구하기
System.out.println("용량의 크기 : " + sb.capacity()); //용량의 크기 구하기
System.out.println("문자열 역순 변경 : " + sb.reverse()); //문자열 뒤집기
System.out.println("마지막 상태 : " + sb); //마지막상태 : kjihgfedcba
}
}
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