The Java String razred charAt() metoda vrne vrednost char pri dani številki indeksa .
Številka indeksa se začne od 0 in sega do n-1, kjer je n dolžina niza. Vrača se StringIndexOutOfBoundsException, če je dano indeksno število večje ali enako tej dolžini niza ali negativno število.
Sintaksa
public char charAt(int index)
Metoda sprejema kazalo kot parameter. Začetni indeks je 0. Vrne znak na določenem mestu indeksa v nizu. Vrže StringIndexOutOfBoundsException če je indeks negativna vrednost ali večji od te dolžine niza.
Določeno s strani
CharSequence vmesnik, ki se nahaja znotraj paketa java.lang.
Notranja izvedba
public char charAt(int index) { if ((index = value.length)) { throw new StringIndexOutOfBoundsException(index); } return value[index]; } Primeri metode Java String charAt().
Oglejmo si program Java, povezan z nizom, v katerem bomo uporabili metodo charAt(), ki izvede neko operacijo na danem nizu.
Ime datoteke: CharAtExample.java
public class CharAtExample{ public static void main(String args[]){ String name='javatpoint'; char ch=name.charAt(4);//returns the char value at the 4th index System.out.println(ch); }} Preizkusite zdaj Izhod:
t
Oglejmo si primer metode charAt(), kjer posredujemo večjo vrednost indeksa. V takem primeru vrže StringIndexOutOfBoundsException med izvajanjem.
Ime datoteke: CharAtExample.java
public class CharAtExample{ public static void main(String args[]){ String name='javatpoint'; char ch=name.charAt(10);//returns the char value at the 10th index System.out.println(ch); }} Izhod:
Exception in thread 'main' java.lang.StringIndexOutOfBoundsException: String index out of range: 10 at java.lang.String.charAt(String.java:658) at CharAtExample.main(CharAtExample.java:4)
Dostop do prvega in zadnjega znaka z uporabo metode charAt().
Oglejmo si preprost primer, kjer dostopamo do prvega in zadnjega znaka iz podanega niza.
Ime datoteke: CharAtExample3.java
public class CharAtExample3 { public static void main(String[] args) { String str = 'Welcome to Javatpoint portal'; int strLength = str.length(); // Fetching first character System.out.println('Character at 0 index is: '+ str.charAt(0)); // The last Character is present at the string length-1 index System.out.println('Character at last index is: '+ str.charAt(strLength-1)); } } Izhod:
Character at 0 index is: W Character at last index is: l
Natisnite znake, predstavljene na čudnih položajih z uporabo metode charAt().
Oglejmo si primer, kjer dostopamo do vseh elementov, ki so prisotni z lihim indeksom.
Ime datoteke: CharAtExample4.java
public class CharAtExample4 { public static void main(String[] args) { String str = 'Welcome to Javatpoint portal'; for (int i=0; i<=str.length()-1; i++) { if(i%2!="0)" system.out.println('char at '+i+' place '+str.charat(i)); } < pre> <p> <strong>Output:</strong> </p> <pre> Char at 1 place e Char at 3 place c Char at 5 place m Char at 7 place Char at 9 place o Char at 11 place J Char at 13 place v Char at 15 place t Char at 17 place o Char at 19 place n Char at 21 place Char at 23 place o Char at 25 place t Char at 27 place l </pre> <p>The position such as 7 and 21 denotes the space.</p> <h3>Counting Frequency of a character in a String by Using the charAt() Method</h3> <p>Let's see an example in which we are counting frequency of a character in the given string.</p> <p> <strong>FileName:</strong> CharAtExample5.java</p> <pre> public class CharAtExample5 { public static void main(String[] args) { String str = 'Welcome to Javatpoint portal'; int count = 0; for (int i=0; i<=str.length()-1; i++) { if(str.charat(i)="=" 't') count++; } system.out.println('frequency of t is: '+count); < pre> <p> <strong>Output:</strong> </p> <pre> Frequency of t is: 4 </pre> <h3>Counting the Number of Vowels in a String by Using the chatAt() Method</h3> <p>Let's see an example where we are counting the number of vowels present in a string with the help of the charAt() method.</p> <p> <strong>FileName:</strong> CharAtExample6.java</p> <pre> // import statement import java.util.*; public class CharAtExample6 { ArrayList al; // constructor for creating and // assigning values to the ArrayList al CharAtExample6() { al = new ArrayList(); al.add('A'); al.add('E'); al.add('a'); al.add('e'); al.add('I'); al.add('O'); al.add('i'); al.add('o'); al.add('U'); al.add('u'); } // a method that checks whether the character c is a vowel or not private boolean isVowel(char c) { for(int i = 0; i <al.size(); 1 i++) { if(c="=" al.get(i)) return true; } false; a method that calculates vowels in the string s public int countvowels(string s) countvowel="0;" store total number of size="s.length();" for(int j="0;" < size; j++) char c="s.charAt(j);" if(isvowel(c)) vowel found! increase count by + 1; countvowel; main static void main(string argvs[]) creating an object class charatexample6 obj="new" charatexample6(); str="Javatpoint is a great site for learning Java." ; noofvowel="obj.countVowels(str);" system.out.println('string: ' str); system.out.println('total are: '+ '
'); noofvowel); pre> <p> <strong>Output:</strong> </p> <pre> String: Javatpoint is a great site for learning Java. Total number of vowels in the string are: 16 String: One apple in a day keeps doctor away. Total number of vowels in the string are: 13 </pre> <hr></al.size();></pre></=str.length()-1;></pre></=str.length()-1;> Položaj, kot sta 7 in 21, označuje prostor.
Štetje pogostosti znaka v nizu z uporabo metode charAt().
Oglejmo si primer, v katerem štejemo pogostost znaka v danem nizu.
Ime datoteke: CharAtExample5.java
public class CharAtExample5 { public static void main(String[] args) { String str = 'Welcome to Javatpoint portal'; int count = 0; for (int i=0; i<=str.length()-1; i++) { if(str.charat(i)="=" \'t\') count++; } system.out.println(\'frequency of t is: \'+count); < pre> <p> <strong>Output:</strong> </p> <pre> Frequency of t is: 4 </pre> <h3>Counting the Number of Vowels in a String by Using the chatAt() Method</h3> <p>Let's see an example where we are counting the number of vowels present in a string with the help of the charAt() method.</p> <p> <strong>FileName:</strong> CharAtExample6.java</p> <pre> // import statement import java.util.*; public class CharAtExample6 { ArrayList al; // constructor for creating and // assigning values to the ArrayList al CharAtExample6() { al = new ArrayList(); al.add('A'); al.add('E'); al.add('a'); al.add('e'); al.add('I'); al.add('O'); al.add('i'); al.add('o'); al.add('U'); al.add('u'); } // a method that checks whether the character c is a vowel or not private boolean isVowel(char c) { for(int i = 0; i <al.size(); 1 i++) { if(c="=" al.get(i)) return true; } false; a method that calculates vowels in the string s public int countvowels(string s) countvowel="0;" store total number of size="s.length();" for(int j="0;" < size; j++) char c="s.charAt(j);" if(isvowel(c)) vowel found! increase count by + 1; countvowel; main static void main(string argvs[]) creating an object class charatexample6 obj="new" charatexample6(); str="Javatpoint is a great site for learning Java." ; noofvowel="obj.countVowels(str);" system.out.println(\'string: \' str); system.out.println(\'total are: \'+ \'
\'); noofvowel); pre> <p> <strong>Output:</strong> </p> <pre> String: Javatpoint is a great site for learning Java. Total number of vowels in the string are: 16 String: One apple in a day keeps doctor away. Total number of vowels in the string are: 13 </pre> <hr></al.size();></pre></=str.length()-1;> Štetje števila samoglasnikov v nizu z uporabo metode chatAt().
Oglejmo si primer, kjer s pomočjo metode charAt() štejemo število samoglasnikov v nizu.
Ime datoteke: CharAtExample6.java
// import statement import java.util.*; public class CharAtExample6 { ArrayList al; // constructor for creating and // assigning values to the ArrayList al CharAtExample6() { al = new ArrayList(); al.add('A'); al.add('E'); al.add('a'); al.add('e'); al.add('I'); al.add('O'); al.add('i'); al.add('o'); al.add('U'); al.add('u'); } // a method that checks whether the character c is a vowel or not private boolean isVowel(char c) { for(int i = 0; i <al.size(); 1 i++) { if(c="=" al.get(i)) return true; } false; a method that calculates vowels in the string s public int countvowels(string s) countvowel="0;" store total number of size="s.length();" for(int j="0;" < size; j++) char c="s.charAt(j);" if(isvowel(c)) vowel found! increase count by + 1; countvowel; main static void main(string argvs[]) creating an object class charatexample6 obj="new" charatexample6(); str="Javatpoint is a great site for learning Java." ; noofvowel="obj.countVowels(str);" system.out.println(\'string: \' str); system.out.println(\'total are: \'+ \'
\'); noofvowel); pre> <p> <strong>Output:</strong> </p> <pre> String: Javatpoint is a great site for learning Java. Total number of vowels in the string are: 16 String: One apple in a day keeps doctor away. Total number of vowels in the string are: 13 </pre> <hr></al.size();>