ה Java String substring() השיטה מחזירה חלק מהמחרוזת.
אנו מעבירים את מיקום המספר beginIndex ו-endIndex בשיטת Java substring כאשר beginIndex הוא כולל, ו-endIndex הוא בלעדי. במילים אחרות, ה-startIndex מתחיל מ-0, ואילו endIndex מתחיל מ-1.
ישנם שני סוגים של שיטות תת-מחרוזת במחרוזת Java.
חֲתִימָה
public String substring(int startIndex) // type - 1 and public String substring(int startIndex, int endIndex) // type - 2
אם לא נציין את endIndex, השיטה תחזיר את כל התווים מ-startIndex.
פרמטרים
startIndex : אינדקס התחלתי כולל
EndIndex : אינדקס סיום הוא בלעדי
החזרות
מחרוזת שצוינה
חריג זריקות
StringIndexOutOfBoundsException נזרק כאשר מתקיים אחד מהתנאים הבאים.
- אם מדד ההתחלה הוא ערך שלילי
- מדד הקצה נמוך מהמדד ההתחלתי.
- האינדקס ההתחלתי או הסיום גדול מהמספר הכולל של התווים הקיימים במחרוזת.
מחרוזת משנה יישום (int beginIndex)
public String substring(int beginIndex) { if (beginIndex <0) { throw new stringindexoutofboundsexception(beginindex); } int sublen="value.length" - beginindex; if (sublen < 0) stringindexoutofboundsexception(sublen); return (beginindex="=" ? this : string(value, beginindex, sublen); pre> <h3>Internal implementation substring(int beginIndex, int endIndex) </h3> <pre> public String substring(int beginIndex, int endIndex) { if (beginIndex value.length) { throw new StringIndexOutOfBoundsException(endIndex); } int subLen = endIndex - beginIndex; if (subLen <0) { throw new stringindexoutofboundsexception(sublen); } return ((beginindex="=" 0) && (endindex="=" value.length)) ? this : string(value, beginindex, sublen); < pre> <h2>Java String substring() method example</h2> <p> <strong>FileName:</strong> SubstringExample.java</p> <pre> public class SubstringExample{ public static void main(String args[]){ String s1='javatpoint'; System.out.println(s1.substring(2,4));//returns va System.out.println(s1.substring(2));//returns vatpoint }} </pre> <span> Test it Now </span> <p> <strong>Output:</strong> </p> <pre>va vatpoint </pre> <h2>Java String substring() Method Example 2</h2> <p> <strong>FileName:</strong> SubstringExample2.java</p> <pre> public class SubstringExample2 { public static void main(String[] args) { String s1='Javatpoint'; String substr = s1.substring(0); // Starts with 0 and goes to end System.out.println(substr); String substr2 = s1.substring(5,10); // Starts from 5 and goes to 10 System.out.println(substr2); String substr3 = s1.substring(5,15); // Returns Exception } } </pre> <p> <strong>Output:</strong> </p> <pre> Javatpoint point Exception in thread 'main' java.lang.StringIndexOutOfBoundsException: begin 5, end 15, length 10 </pre> <h2>Applications of substring() Method</h2> <p>1) The substring() method can be used to do some prefix or suffix extraction. For example, we can have a list of names, and it is required to filter out names with surname as 'singh'. The following program shows the same.</p> <p> <strong>FileName:</strong> SubstringExample3.java</p> <pre> public class SubstringExample3 { // main method public static void main(String argvs[]) { String str[] = { 'Praveen Kumar', 'Yuvraj Singh', 'Harbhajan Singh', 'Gurjit Singh', 'Virat Kohli', 'Rohit Sharma', 'Sandeep Singh', 'Milkha Singh' }; String surName = 'Singh'; int surNameSize = surName.length(); int size = str.length; for(int j = 0; j <size; j++) { int length="str[j].length();" extracting the surname string substr="str[j].substring(length" - surnamesize); checks whether is equal to 'singh' or not if(substr.equals(surname)) system.out.println(str[j]); } < pre> <p> <strong>Output:</strong> </p> <pre> Yuvraj Singh Harbhajan Singh Gurjit Singh Sandeep Singh Milkha Singh </pre> <p>2) The substring() method can also be used to check whether a string is a palindrome or not.</p> <p> <strong>FileName:</strong> SubstringExample4.java</p> <pre> public class SubstringExample4 { public boolean isPalindrome(String str) { int size = str.length(); // handling the base case if(size == 0 || size == 1) { // an empty string // or a string of only one character // is always a palindrome return true; } String f = str.substring(0, 1); String l = str.substring(size - 1); // comparing first and the last character of the string if(l.equals(f)) { // recursively finding the solution using the substring() method // reducing the number of characters of the by 2 for the next recursion return isPalindrome(str.substring(1, size - 1)); } return false; } // main method public static void main(String argvs[]) { // instantiating the class SubstringExample4 SubstringExample4 obj = new SubstringExample4(); String str[] = { 'madam', 'rock', 'eye', 'noon', 'kill' }; int size = str.length; for(int j = 0; j <size; j++) { if(obj.ispalindrome(str[j])) system.out.println(str[j] + ' is a palindrome.'); } else not < pre> <p> <strong>Output:</strong> </p> <pre> madam is a palindrome. rock is not a palindrome. eye is a palindrome. noon is a palindrome. kill is not a palindrome. </pre> <hr></size;></pre></size;></pre></0)></pre></0)> בדוק את זה עכשיו תְפוּקָה:
va vatpoint
Java String substring() שיטה דוגמה 2
שם קובץ: SubstringExample2.java
public class SubstringExample2 { public static void main(String[] args) { String s1='Javatpoint'; String substr = s1.substring(0); // Starts with 0 and goes to end System.out.println(substr); String substr2 = s1.substring(5,10); // Starts from 5 and goes to 10 System.out.println(substr2); String substr3 = s1.substring(5,15); // Returns Exception } } תְפוּקָה:
Javatpoint point Exception in thread 'main' java.lang.StringIndexOutOfBoundsException: begin 5, end 15, length 10
יישומים של substring() Method
1) ניתן להשתמש בשיטת substring() כדי לבצע חילוץ של קידומת או סיומת. לדוגמה, אנחנו יכולים לקבל רשימה של שמות, ויש צורך לסנן שמות עם שם משפחה בתור 'סינג'. התוכנית הבאה מציגה את אותו הדבר.
שם קובץ: SubstringExample3.java
public class SubstringExample3 { // main method public static void main(String argvs[]) { String str[] = { 'Praveen Kumar', 'Yuvraj Singh', 'Harbhajan Singh', 'Gurjit Singh', 'Virat Kohli', 'Rohit Sharma', 'Sandeep Singh', 'Milkha Singh' }; String surName = 'Singh'; int surNameSize = surName.length(); int size = str.length; for(int j = 0; j <size; j++) { int length="str[j].length();" extracting the surname string substr="str[j].substring(length" - surnamesize); checks whether is equal to \'singh\' or not if(substr.equals(surname)) system.out.println(str[j]); } < pre> <p> <strong>Output:</strong> </p> <pre> Yuvraj Singh Harbhajan Singh Gurjit Singh Sandeep Singh Milkha Singh </pre> <p>2) The substring() method can also be used to check whether a string is a palindrome or not.</p> <p> <strong>FileName:</strong> SubstringExample4.java</p> <pre> public class SubstringExample4 { public boolean isPalindrome(String str) { int size = str.length(); // handling the base case if(size == 0 || size == 1) { // an empty string // or a string of only one character // is always a palindrome return true; } String f = str.substring(0, 1); String l = str.substring(size - 1); // comparing first and the last character of the string if(l.equals(f)) { // recursively finding the solution using the substring() method // reducing the number of characters of the by 2 for the next recursion return isPalindrome(str.substring(1, size - 1)); } return false; } // main method public static void main(String argvs[]) { // instantiating the class SubstringExample4 SubstringExample4 obj = new SubstringExample4(); String str[] = { 'madam', 'rock', 'eye', 'noon', 'kill' }; int size = str.length; for(int j = 0; j <size; j++) { if(obj.ispalindrome(str[j])) system.out.println(str[j] + \' is a palindrome.\'); } else not < pre> <p> <strong>Output:</strong> </p> <pre> madam is a palindrome. rock is not a palindrome. eye is a palindrome. noon is a palindrome. kill is not a palindrome. </pre> <hr></size;></pre></size;> 2) ניתן להשתמש בשיטת substring() גם כדי לבדוק אם מחרוזת היא פלינדרום או לא.
שם קובץ: SubstringExample4.java
public class SubstringExample4 { public boolean isPalindrome(String str) { int size = str.length(); // handling the base case if(size == 0 || size == 1) { // an empty string // or a string of only one character // is always a palindrome return true; } String f = str.substring(0, 1); String l = str.substring(size - 1); // comparing first and the last character of the string if(l.equals(f)) { // recursively finding the solution using the substring() method // reducing the number of characters of the by 2 for the next recursion return isPalindrome(str.substring(1, size - 1)); } return false; } // main method public static void main(String argvs[]) { // instantiating the class SubstringExample4 SubstringExample4 obj = new SubstringExample4(); String str[] = { 'madam', 'rock', 'eye', 'noon', 'kill' }; int size = str.length; for(int j = 0; j <size; j++) { if(obj.ispalindrome(str[j])) system.out.println(str[j] + \\' is a palindrome.\\'); } else not < pre> <p> <strong>Output:</strong> </p> <pre> madam is a palindrome. rock is not a palindrome. eye is a palindrome. noon is a palindrome. kill is not a palindrome. </pre> <hr></size;>