안녕하세요 오늘은 자바에 문자열 클레스인 String 에 대해서 알아보겠습니다.
막상 프로그래밍을 시작하면 자주 사용하는 클레스중 하나인 String 은
char 를 배열로 표현한 배열이라고 생각하시면 쉽습니다.
모든 클래스는 속성 +메소드 로 이루어저 있습니다.
일단 String 이 가지는 속성은 없다고 보시면 됩니다.
생성자
Constructor and Description |
---|
String()
Initializes a newly created String object so that it represents an empty character sequence. |
String(byte[] bytes)
Constructs a new String by decoding the specified array of bytes using the platform's default charset. |
String(byte[] bytes, Charset charset)
|
String(byte[] ascii, int hibyte)
Deprecated.
This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the String constructors that take a Charset , charset name, or that use the platform's default charset. |
String(byte[] bytes, int offset, int length)
Constructs a new String by decoding the specified subarray of bytes using the platform's default charset. |
String(byte[] bytes, int offset, int length, Charset charset)
|
String(byte[] ascii, int hibyte, int offset, int count)
Deprecated.
This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the String constructors that take a Charset , charset name, or that use the platform's default charset. |
String(byte[] bytes, int offset, int length, String charsetName)
Constructs a new String by decoding the specified subarray of bytes using the specified charset. |
String(byte[] bytes, String charsetName)
|
String(char[] value)
Allocates a new String so that it represents the sequence of characters currently contained in the character array argument. |
String(char[] value, int offset, int count)
Allocates a new String that contains characters from a subarray of the character array argument. |
String(int[] codePoints, int offset, int count)
Allocates a new String that contains characters from a subarray of the Unicode code point array argument. |
String(String original)
Initializes a newly created String object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string. |
String(StringBuffer buffer)
Allocates a new string that contains the sequence of characters currently contained in the string buffer argument. |
String(StringBuilder builder)
Allocates a new string that contains the sequence of characters currently contained in the string builder argument. |
메서드
Modifier and Type | Method and Description |
---|---|
char |
charAt(int index)
Returns the char value at the specified index. |
int |
codePointAt(int index)
Returns the character (Unicode code point) at the specified index. |
int |
codePointBefore(int index)
Returns the character (Unicode code point) before the specified index. |
int |
codePointCount(int beginIndex, int endIndex)
Returns the number of Unicode code points in the specified text range of this String . |
int |
compareTo(String anotherString)
Compares two strings lexicographically. |
int |
compareToIgnoreCase(String str)
Compares two strings lexicographically, ignoring case differences. |
String |
concat(String str)
Concatenates the specified string to the end of this string. |
boolean |
contains(CharSequence s)
Returns true if and only if this string contains the specified sequence of char values. |
boolean |
contentEquals(CharSequence cs)
Compares this string to the specified CharSequence . |
boolean |
contentEquals(StringBuffer sb)
Compares this string to the specified StringBuffer . |
static String |
copyValueOf(char[] data)
Returns a String that represents the character sequence in the array specified. |
static String |
copyValueOf(char[] data, int offset, int count)
Returns a String that represents the character sequence in the array specified. |
boolean |
endsWith(String suffix)
Tests if this string ends with the specified suffix. |
boolean |
equals(Object anObject)
Compares this string to the specified object. |
boolean |
equalsIgnoreCase(String anotherString)
Compares this String to another String , ignoring case considerations. |
static String |
format(Locale l, String format, Object... args)
Returns a formatted string using the specified locale, format string, and arguments. |
static String |
format(String format, Object... args)
Returns a formatted string using the specified format string and arguments. |
byte[] |
getBytes()
Encodes this String into a sequence of bytes using the platform's default charset, storing the result into a new byte array. |
byte[] |
getBytes(Charset charset)
Encodes this String into a sequence of bytes using the given charset, storing the result into a new byte array. |
void |
getBytes(int srcBegin, int srcEnd, byte[] dst, int dstBegin)
Deprecated.
This method does not properly convert characters into bytes. As of JDK 1.1, the preferred way to do this is via the getBytes() method, which uses the platform's default charset. |
byte[] |
getBytes(String charsetName)
Encodes this String into a sequence of bytes using the named charset, storing the result into a new byte array. |
void |
getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)
Copies characters from this string into the destination character array. |
int |
hashCode()
Returns a hash code for this string. |
int |
indexOf(int ch)
Returns the index within this string of the first occurrence of the specified character. |
int |
indexOf(int ch, int fromIndex)
Returns the index within this string of the first occurrence of the specified character, starting the search at the specified index. |
int |
indexOf(String str)
Returns the index within this string of the first occurrence of the specified substring. |
int |
indexOf(String str, int fromIndex)
Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. |
String |
intern()
Returns a canonical representation for the string object. |
boolean |
isEmpty()
|
int |
lastIndexOf(int ch)
Returns the index within this string of the last occurrence of the specified character. |
int |
lastIndexOf(int ch, int fromIndex)
Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index. |
int |
lastIndexOf(String str)
Returns the index within this string of the last occurrence of the specified substring. |
int |
lastIndexOf(String str, int fromIndex)
Returns the index within this string of the last occurrence of the specified substring, searching backward starting at the specified index. |
int |
length()
Returns the length of this string. |
boolean |
matches(String regex)
Tells whether or not this string matches the given regular expression. |
int |
offsetByCodePoints(int index, int codePointOffset)
Returns the index within this String that is offset from the given index by codePointOffset code points. |
boolean |
regionMatches(boolean ignoreCase, int toffset, String other, int ooffset, int len)
Tests if two string regions are equal. |
boolean |
regionMatches(int toffset, String other, int ooffset, int len)
Tests if two string regions are equal. |
String |
replace(char oldChar, char newChar)
Returns a new string resulting from replacing all occurrences of oldChar in this string with newChar . |
String |
replace(CharSequence target, CharSequence replacement)
Replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence. |
String |
replaceAll(String regex, String replacement)
Replaces each substring of this string that matches the given regular expression with the given replacement. |
String |
replaceFirst(String regex, String replacement)
Replaces the first substring of this string that matches the given regular expression with the given replacement. |
String[] |
split(String regex)
Splits this string around matches of the given regular expression. |
String[] |
split(String regex, int limit)
Splits this string around matches of the given regular expression. |
boolean |
startsWith(String prefix)
Tests if this string starts with the specified prefix. |
boolean |
startsWith(String prefix, int toffset)
Tests if the substring of this string beginning at the specified index starts with the specified prefix. |
CharSequence |
subSequence(int beginIndex, int endIndex)
Returns a new character sequence that is a subsequence of this sequence. |
String |
substring(int beginIndex)
Returns a new string that is a substring of this string. |
String |
substring(int beginIndex, int endIndex)
Returns a new string that is a substring of this string. |
char[] |
toCharArray()
Converts this string to a new character array. |
String |
toLowerCase()
Converts all of the characters in this String to lower case using the rules of the default locale. |
String |
toLowerCase(Locale locale)
Converts all of the characters in this String to lower case using the rules of the given Locale . |
String |
toString()
This object (which is already a string!) is itself returned. |
String |
toUpperCase()
Converts all of the characters in this String to upper case using the rules of the default locale. |
String |
toUpperCase(Locale locale)
Converts all of the characters in this String to upper case using the rules of the given Locale . |
String |
trim()
Returns a copy of the string, with leading and trailing whitespace omitted. |
static String |
valueOf(boolean b)
Returns the string representation of the boolean argument. |
static String |
valueOf(char c)
Returns the string representation of the char argument. |
static String |
valueOf(char[] data)
Returns the string representation of the char array argument. |
static String |
valueOf(char[] data, int offset, int count)
Returns the string representation of a specific subarray of the char array argument. |
static String |
valueOf(double d)
Returns the string representation of the double argument. |
static String |
valueOf(float f)
Returns the string representation of the float argument. |
static String |
valueOf(int i)
Returns the string representation of the int argument. |
static String |
valueOf(long l)
Returns the string representation of the long argument. |
static String |
valueOf(Object obj)
Returns the string representation of the Object argument. |
그러면 위의 내용을 가지고 일반적으로 자주 사용되는 예시를 보여드리겠습니다.
ch배열과 String의 비교
public class StringExample{
public static void main(String args[]){
String s1="java";//creating string by java string literal
char ch[]={'s','t','r','i','n','g','s'};
String s2=new String(ch);//converting char array to string
String s3=new String("example");//creating java string by new keyword
System.out.println(s1);
System.out.println(s2);
System.out.println(s3);
}
}
문자열 연결 메서드
class Testimmutablestring1{
public static void main(String args[]){
String s="Sachin";
s=s.concat(" Tendulkar");
System.out.println(s);
}
}
문자열 값 비교 equals 사용법
class Teststringcomparison1{
public static void main(String args[]){
String s1="Sachin";
String s2="Sachin";
String s3=new String("Sachin");
String s4="Saurav";
System.out.println(s1.equals(s2));//true
System.out.println(s1.equals(s3));//true
System.out.println(s1.equals(s4));//false
}
}
문자열 주소 값 비교
class Teststringcomparison3{
public static void main(String args[]){
String s1="Sachin";
String s2="Sachin";
String s3=new String("Sachin");
System.out.println(s1==s2);//true (because both refer to same instance)
System.out.println(s1==s3);//false(because s3 refers to instance created in nonpool)
}
}
Substring 사용법
public class TestSubstring{
public static void main(String args[]){
String s="SachinTendulkar";
System.out.println(s.substring(6));//Tendulkar
System.out.println(s.substring(0,6));//Sachin
}
}
public class LastTest{
public static void main(String args[]){
String s="Sachin";
System.out.println(s.toUpperCase());//SACHIN
System.out.println(s.toLowerCase());//sachin
System.out.println(s);//Sachin(no change in original)
String s=" Sachin ";
System.out.println(s);// Sachin
System.out.println(s.trim());//Sachin
String s="Sachin";
System.out.println(s.startsWith("Sa"));//true
System.out.println(s.endsWith("n"));//true
String s="Sachin";
System.out.println(s.charAt(0));//S
System.out.println(s.charAt(3));//h
String s="Sachin";
System.out.println(s.length());//6
String s=new String("Sachin");
String s2=s.intern();
System.out.println(s2);//Sachin
int a=10;
String s=String.valueOf(a);
System.out.println(s+10);
String s1="Java is a programming language. Java is a platform. Java is an Island.";
String replaceString=s1.replace("Java","Kava");//replaces all occurrences of "Java" to "Kava"
System.out.println(replaceString);
}
}
이상으로 String 클래스를 마치겠습니다 . 다음에는 유사 클레스인 StringBuffer로 돌아오겠습니다.
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