The Java String klasa compareTo() metoda leksikografski uspoređuje dati niz s trenutnim nizom. Vraća pozitivan broj, negativan broj ili 0.
Uspoređuje nizove na temelju Unicode vrijednosti svakog znaka u nizovima.
Ako je prvi niz leksikografski veći od drugog niza, vraća pozitivan broj (razlika vrijednosti znaka). Ako je prvi niz leksikografski manji od drugog niza, vraća negativan broj, a ako je prvi niz leksikografski jednak drugom nizu, vraća 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 prihvaća parametar tipa String koji treba usporediti s trenutnim nizom.
Vraća cjelobrojnu vrijednost. Dopušta sljedeće dvije iznimke:
ClassCastException: Ako se ovaj objekt ne može usporediti s navedenim objektom.
NullPointerException: Ako je navedeni objekt null.
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Interna implementacija
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)>Testirajte sada
Izlaz:
0 -5 -1 2
Java String compareTo(): prazan niz
Kada uspoređujemo dva niza u kojima je prvi ili drugi niz prazan, metoda vraća duljinu niza. Dakle, mogu postojati dva scenarija:
- Ako prvi string je prazan niz, metoda vraća a negativan
- Ako drugi string je prazan niz, metoda vraća a pozitivan broj koji je duljina prvog niza.
Naziv datoteke: 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)); }}Testirajte sada
Izlaz:
5 -2
Java String compareTo(): osjetljivo na velika i mala slova
Kako bismo provjerili uzima li metoda compareTo() u obzir osjetljivost znakova na velika i mala slova ili ne, napravit ćemo usporedbu između dva niza koji sadrže ista slova u istom nizu.
Pretpostavimo da niz ima velika slova, a drugi niz ima mala slova. Pri usporedbi ova dva niza, ako je rezultat 0, tada metoda compareTo() ne uzima u obzir osjetljivost znakova na velika i mala slova; inače, metoda uzima u obzir osjetljivost znakova na velika i mala slova.
Naziv datoteke: CompareToExample3.java
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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)); } }
Izlaz:
-32
Zaključak: Gledajući izlaz, očito je da ishod nije jednak nuli. Stoga se metoda compareTo() brine o osjetljivosti znakova na velika i mala slova.
Java String compareTo(): ClassCastException
The ClassCastException izbacuje se kada se uspoređuju objekti nekompatibilnih tipova. U sljedećem primjeru uspoređujemo objekt ArrayList (al) s literalom niza ('Sehwag').
Naziv datoteke: 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); } }
Izlaz:
Exception in thread 'main' java.lang.ClassCastException: class Players cannot be cast to class java.lang.Comparable
Java String compareTo(): NullPointerException
NullPointerException se javlja kada null objekt pozove metodu compareTo(). Promatrajte sljedeći primjer.
Naziv datoteke: 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); } }
Izlaz:
Exception in thread 'main' java.lang.NullPointerException at CompareToExample5.main(CompareToExample5.java:9)