[13] JAVA String 클래스 메소드 정리

String Methods

 

1. int length(): Returns the number of characters in the String.

"GeeksforGeeks".length();  // returns 13

 

2. Char charAt(int i): Returns the character at ith index.

"GeeksforGeeks".charAt(3); // returns  ‘k’

 

3. String substring (int i): Return the substring from the ith  index character to end.

"GeeksforGeeks".substring(3); // returns “ksforGeeks”

 

4. String substring (int i, int j): Returns the substring from i to j-1 index.

 "GeeksforGeeks".substring(2, 5); // returns “eks”

 

5. String concat( String str): Concatenates specified string to the end of this string. (문자열 연결)

 String s1 = ”Geeks”;
 String s2 = ”forGeeks”;
 String output = s1.concat(s2); // returns “GeeksforGeeks”

 

6. int indexOf (String s): Returns the index within the string of the first occurrence of the specified string.

 String s = ”Learn Share Learn”;
 int output = s.indexOf(“Share”); // returns 6

 

7. int indexOf (String s, int i): Returns the index within the string of the first occurrence of the specified string, starting at the specified index.

 String s = ”Learn Share Learn”;
 int output = s.indexOf("ea",3);// returns 13

 

8. Int lastIndexOf( String s): Returns the index within the string of the last occurrence of the specified string.

 String s = ”Learn Share Learn”;
 int output = s.lastIndexOf("a"); // returns 14

 

9. boolean equals( Object otherObj): Compares this string to the specified object.

 Boolean out = “Geeks”.equals(“Geeks”); // returns true
 Boolean out = “Geeks”.equals(“geeks”); // returns false

 

10. boolean  equalsIgnoreCase (String anotherString): Compares string to another string, ignoring case considerations.

 Boolean out= “Geeks”.equalsIgnoreCase(“Geeks”); // returns true
 Boolean out = “Geeks”.equalsIgnoreCase(“geeks”); // returns true

 

11.  int compareTo( String anotherString): Compares two string lexicographically.

 int out = s1.compareTo(s2);  // where s1 and s2 are
                             // strings to be compared

 This returns difference s1-s2. If :
 out < 0  // s1 comes before s2
 out = 0  // s1 and s2 are equal.
 out > 0   // s1 comes after s2.

 

11. int compareToIgnoreCase( String anotherString): Compares two string lexicographically, ignoring case considerations.

 int out = s1.compareToIgnoreCase(s2);  
// where s1 and s2 are 
// strings to be compared

 This returns difference s1-s2. If :
 out < 0  // s1 comes before s2
 out = 0   // s1 and s2 are equal.
 out > 0   // s1 comes after s2.

 Note- In this case, it will not consider case of a letter (it will ignore whether it is uppercase or lowercase).

 

 

12. String toLowerCase(): Converts all the characters in the String to lower case.

String word1 = “HeLLo”;
String word3 = word1.toLowerCase(); // returns “hello"

 

13. String toUpperCase(): Converts all the characters in the String to upper case.

String word1 = “HeLLo”;
String word2 = word1.toUpperCase(); // returns “HELLO”

 

14. String trim(): Returns the copy of the String, by removing whitespaces at both ends. It does not affect whitespaces in the middle.

String word1 = “ Learn Share Learn “;
String word2 = word1.trim(); // returns “Learn Share Learn”

 

15. String replace (char oldChar, char newChar): Returns new string by replacing all occurrences of oldChar with newChar.

String s1 = “feeksforfeeks“;
String s2 = “feeksforfeeks”.replace(‘f’ ,’g’); // returns “geeksgorgeeks”

 

 

출처 : https://www.geeksforgeeks.org/string-class-in-java/?ref=gcse 

String class in Java - GeeksforGeeks