The Clasa Java String compareTo() metoda compară lexicografic șirul dat cu șirul curent. Returnează un număr pozitiv, un număr negativ sau 0.
Compară șirurile pe baza valorii Unicode a fiecărui caracter din șiruri.
Dacă primul șir este mai mare din punct de vedere lexicografic decât al doilea șir, acesta returnează un număr pozitiv (diferența de valoare a caracterului). Dacă primul șir este mai mic decât al doilea șir din punct de vedere lexicografic, returnează un număr negativ, iar dacă primul șir este lexicografic egal cu al doilea șir, returnează 0.
if s1 > s2, it returns positive number if s1 <s2, 0 it returns negative number if s1="=" s2, < pre> <h3>Syntax</h3> <pre> public int compareTo(String anotherString) </pre> <p>The method accepts a parameter of type String that is to be compared with the current string.</p> <p>It returns an integer value. It throws the following two exceptions:</p> <p> <strong>ClassCastException:</strong> If this object cannot get compared with the specified object.</p> <p> <strong>NullPointerException:</strong> If the specified object is null.</p> <h2>Internal implementation</h2> <pre> int compareTo(String anotherString) { int length1 = value.length; int length2 = anotherString.value.length; int limit = Math.min(length1, length2); char v1[] = value; char v2[] = anotherString.value; int i = 0; while (i <limit) { char ch1="v1[i];" ch2="v2[i];" if (ch1 !="ch2)" return - ch2; } i++; length1 length2; < pre> <h2>Java String compareTo() Method Example</h2> <p> <strong>FileName:</strong> CompareToExample.java</p> <pre> public class CompareToExample{ public static void main(String args[]){ String s1='hello'; String s2='hello'; String s3='meklo'; String s4='hemlo'; String s5='flag'; System.out.println(s1.compareTo(s2));//0 because both are equal System.out.println(s1.compareTo(s3));//-5 because 'h' is 5 times lower than 'm' System.out.println(s1.compareTo(s4));//-1 because 'l' is 1 times lower than 'm' System.out.println(s1.compareTo(s5));//2 because 'h' is 2 times greater than 'f' }} </pre> <span> Test it Now </span> <p> <strong>Output:</strong> </p> <pre> 0 -5 -1 2 </pre> <h2>Java String compareTo(): empty string</h2> <p>When we compare two strings in which either first or second string is empty, the method returns the length of the string. So, there may be two scenarios:</p> <ul> <li>If <strong>first</strong> string is an empty string, the method returns a <strong>negative</strong> </li> <li>If <strong>second</strong> string is an empty string, the method returns a <strong>positive</strong> number that is the length of the first string.</li> </ul> <p> <strong>FileName:</strong> CompareToExample2.java</p> <pre> public class CompareToExample2{ public static void main(String args[]){ String s1='hello'; String s2=''; String s3='me'; System.out.println(s1.compareTo(s2)); System.out.println(s2.compareTo(s3)); }} </pre> <span> Test it Now </span> <p> <strong>Output:</strong> </p> <pre> 5 -2 </pre> <h3>Java String compareTo(): case sensitive</h3> <p>To check whether the compareTo() method considers the case sensitiveness of characters or not, we will make the comparison between two strings that contain the same letters in the same sequence.</p> <p>Suppose, a string having letters in uppercase, and the second string having the letters in lowercase. On comparing these two string, if the outcome is 0, then the compareTo() method does not consider the case sensitiveness of characters; otherwise, the method considers the case sensitiveness of characters.</p> <p> <strong>FileName:</strong> CompareToExample3.java</p> <pre> public class CompareToExample3 { // main method public static void main(String argvs[]) { // input string in uppercase String st1 = new String('INDIA IS MY COUNTRY'); // input string in lowercase String st2 = new String('india is my country'); System.out.println(st1.compareTo(st2)); } } </pre> <p> <strong>Output:</strong> </p> <pre> -32 </pre> <p> <strong>Conclusion:</strong> It is obvious by looking at the output that the outcome is not equal to zero. Hence, the compareTo() method takes care of the case sensitiveness of characters.</p> <h3>Java String compareTo(): ClassCastException</h3> <p>The <strong>ClassCastException</strong> is thrown when objects of incompatible types get compared. In the following example, we are comparing an object of the ArrayList (al) with a string literal ('Sehwag').</p> <p> <strong>FileName:</strong> CompareToExample4.java</p> <pre> // import statement import java.util.*; class Players { private String name; // constructor of the class public Players(String str) { name = str; } } public class CompareToExample4 { // main method public static void main(String[] args) { Players ronaldo = new Players('Ronaldo'); Players sachin = new Players('Sachin'); Players messi = new Players('Messi'); ArrayList al = new ArrayList(); al.add(ronaldo); al.add(sachin); al.add(messi); // performing binary search on the list al Collections.binarySearch(al, 'Sehwag', null); } } </pre> <p> <strong>Output:</strong> </p> <pre> Exception in thread 'main' java.lang.ClassCastException: class Players cannot be cast to class java.lang.Comparable </pre> <h3>Java String compareTo(): NullPointerException</h3> <p>The NullPointerException is thrown when a null object invokes the compareTo() method. Observe the following example.</p> <p> <strong>FileName:</strong> CompareToExample5.java</p> <pre> public class CompareToExample5 { // main method public static void main(String[] args) { String str = null; // null is invoking the compareTo method. Hence, the NullPointerException // will be raised int no = str.compareTo('India is my country.'); System.out.println(no); } } </pre> <p> <strong>Output:</strong> </p> <pre> Exception in thread 'main' java.lang.NullPointerException at CompareToExample5.main(CompareToExample5.java:9) </pre> <hr></limit)></pre></s2,> Metoda acceptă un parametru de tip String care urmează să fie comparat cu șirul curent.
Returnează o valoare întreagă. Se aruncă următoarele două excepții:
ClassCastException: Dacă acest obiect nu poate fi comparat cu obiectul specificat.
NullPointerException: Dacă obiectul specificat este nul.
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Implementare internă
int compareTo(String anotherString) { int length1 = value.length; int length2 = anotherString.value.length; int limit = Math.min(length1, length2); char v1[] = value; char v2[] = anotherString.value; int i = 0; while (i <limit) { char ch1="v1[i];" ch2="v2[i];" if (ch1 !="ch2)" return - ch2; } i++; length1 length2; < pre> <h2>Java String compareTo() Method Example</h2> <p> <strong>FileName:</strong> CompareToExample.java</p> <pre> public class CompareToExample{ public static void main(String args[]){ String s1='hello'; String s2='hello'; String s3='meklo'; String s4='hemlo'; String s5='flag'; System.out.println(s1.compareTo(s2));//0 because both are equal System.out.println(s1.compareTo(s3));//-5 because 'h' is 5 times lower than 'm' System.out.println(s1.compareTo(s4));//-1 because 'l' is 1 times lower than 'm' System.out.println(s1.compareTo(s5));//2 because 'h' is 2 times greater than 'f' }} </pre> <span> Test it Now </span> <p> <strong>Output:</strong> </p> <pre> 0 -5 -1 2 </pre> <h2>Java String compareTo(): empty string</h2> <p>When we compare two strings in which either first or second string is empty, the method returns the length of the string. So, there may be two scenarios:</p> <ul> <li>If <strong>first</strong> string is an empty string, the method returns a <strong>negative</strong> </li> <li>If <strong>second</strong> string is an empty string, the method returns a <strong>positive</strong> number that is the length of the first string.</li> </ul> <p> <strong>FileName:</strong> CompareToExample2.java</p> <pre> public class CompareToExample2{ public static void main(String args[]){ String s1='hello'; String s2=''; String s3='me'; System.out.println(s1.compareTo(s2)); System.out.println(s2.compareTo(s3)); }} </pre> <span> Test it Now </span> <p> <strong>Output:</strong> </p> <pre> 5 -2 </pre> <h3>Java String compareTo(): case sensitive</h3> <p>To check whether the compareTo() method considers the case sensitiveness of characters or not, we will make the comparison between two strings that contain the same letters in the same sequence.</p> <p>Suppose, a string having letters in uppercase, and the second string having the letters in lowercase. On comparing these two string, if the outcome is 0, then the compareTo() method does not consider the case sensitiveness of characters; otherwise, the method considers the case sensitiveness of characters.</p> <p> <strong>FileName:</strong> CompareToExample3.java</p> <pre> public class CompareToExample3 { // main method public static void main(String argvs[]) { // input string in uppercase String st1 = new String('INDIA IS MY COUNTRY'); // input string in lowercase String st2 = new String('india is my country'); System.out.println(st1.compareTo(st2)); } } </pre> <p> <strong>Output:</strong> </p> <pre> -32 </pre> <p> <strong>Conclusion:</strong> It is obvious by looking at the output that the outcome is not equal to zero. Hence, the compareTo() method takes care of the case sensitiveness of characters.</p> <h3>Java String compareTo(): ClassCastException</h3> <p>The <strong>ClassCastException</strong> is thrown when objects of incompatible types get compared. In the following example, we are comparing an object of the ArrayList (al) with a string literal ('Sehwag').</p> <p> <strong>FileName:</strong> CompareToExample4.java</p> <pre> // import statement import java.util.*; class Players { private String name; // constructor of the class public Players(String str) { name = str; } } public class CompareToExample4 { // main method public static void main(String[] args) { Players ronaldo = new Players('Ronaldo'); Players sachin = new Players('Sachin'); Players messi = new Players('Messi'); ArrayList al = new ArrayList(); al.add(ronaldo); al.add(sachin); al.add(messi); // performing binary search on the list al Collections.binarySearch(al, 'Sehwag', null); } } </pre> <p> <strong>Output:</strong> </p> <pre> Exception in thread 'main' java.lang.ClassCastException: class Players cannot be cast to class java.lang.Comparable </pre> <h3>Java String compareTo(): NullPointerException</h3> <p>The NullPointerException is thrown when a null object invokes the compareTo() method. Observe the following example.</p> <p> <strong>FileName:</strong> CompareToExample5.java</p> <pre> public class CompareToExample5 { // main method public static void main(String[] args) { String str = null; // null is invoking the compareTo method. Hence, the NullPointerException // will be raised int no = str.compareTo('India is my country.'); System.out.println(no); } } </pre> <p> <strong>Output:</strong> </p> <pre> Exception in thread 'main' java.lang.NullPointerException at CompareToExample5.main(CompareToExample5.java:9) </pre> <hr></limit)> Testează-l acum Ieșire:
0 -5 -1 2
Java String compareTo(): șir gol
Când comparăm două șiruri în care primul sau al doilea șir este gol, metoda returnează lungimea șirului. Deci, pot exista două scenarii:
- Dacă primul șir este un șir gol, metoda returnează a negativ
- Dacă al doilea șir este un șir gol, metoda returnează a pozitiv număr care este lungimea primului șir.
Nume de fișier: CompareToExample2.java
public class CompareToExample2{ public static void main(String args[]){ String s1='hello'; String s2=''; String s3='me'; System.out.println(s1.compareTo(s2)); System.out.println(s2.compareTo(s3)); }} Testează-l acum Ieșire:
5 -2
Java String compareTo(): diferențiază majuscule și minuscule
Pentru a verifica dacă metoda compareTo() ia în considerare sensibilitatea majusculelor sau nu a caracterelor, vom face comparația între două șiruri care conțin aceleași litere în aceeași secvență.
Să presupunem că un șir are literele mari, iar al doilea șir are literele cu litere mici. La compararea acestor două șiruri de caractere, dacă rezultatul este 0, atunci metoda compareTo() nu ia în considerare sensibilitatea caracterelor cu majuscule și minuscule; în caz contrar, metoda ia în considerare caracterele sensibile la majuscule și minuscule.
Nume de fișier: CompareToExample3.java
public class CompareToExample3 { // main method public static void main(String argvs[]) { // input string in uppercase String st1 = new String('INDIA IS MY COUNTRY'); // input string in lowercase String st2 = new String('india is my country'); System.out.println(st1.compareTo(st2)); } } Ieșire:
-32
Concluzie: Este evident, analizând rezultatul, că rezultatul nu este egal cu zero. Prin urmare, metoda compareTo() are grijă de sensibilitatea caracterelor cu majuscule și minuscule.
Java String compareTo(): ClassCastException
The ClassCastException este aruncat atunci când obiecte de tipuri incompatibile sunt comparate. În exemplul următor, comparăm un obiect din ArrayList (al) cu un șir literal ('Sehwag').
Nume de fișier: CompareToExample4.java
// import statement import java.util.*; class Players { private String name; // constructor of the class public Players(String str) { name = str; } } public class CompareToExample4 { // main method public static void main(String[] args) { Players ronaldo = new Players('Ronaldo'); Players sachin = new Players('Sachin'); Players messi = new Players('Messi'); ArrayList al = new ArrayList(); al.add(ronaldo); al.add(sachin); al.add(messi); // performing binary search on the list al Collections.binarySearch(al, 'Sehwag', null); } } Ieșire:
Exception in thread 'main' java.lang.ClassCastException: class Players cannot be cast to class java.lang.Comparable
Java String compareTo(): NullPointerException
NullPointerException este lansată atunci când un obiect nul invocă metoda compareTo(). Observați următorul exemplu.
boolean la șir
Nume de fișier: CompareToExample5.java
public class CompareToExample5 { // main method public static void main(String[] args) { String str = null; // null is invoking the compareTo method. Hence, the NullPointerException // will be raised int no = str.compareTo('India is my country.'); System.out.println(no); } } Ieșire:
Exception in thread 'main' java.lang.NullPointerException at CompareToExample5.main(CompareToExample5.java:9)