Carane nggunakake penunjuk fungsi ing Jawa
Sumber: Dev.to Pointers minangka obyek sing nyimpen alamat memori lan bisa nyimpen memori kanthi langsung ngarahake menyang obyek target, array, utawa alamat variabel tinimbang ngliwati nilai. Sayange, ora ana konsep "nyata" pitunjuk ing Jawa. Nanging untunge kanggo kita, ana solusi nggunakake referensi metode sing cedhak karo sing nyata.
Pitunjuk fungsi
Pointer fungsi minangka pointer sing nuduhake alamat fungsi. Sawetara kasus panggunaan kalebu nggawe rutin callback kanthi nggawe fungsi sing nelpon fungsi liyane adhedhasar eksekusi, utawa nyimpen macem-macem penunjuk fungsi kanggo metode sing diarani kanthi dinamis (contone, nyimpen instruksi prosesor kanggo emulator).Simulasi pointer fungsi
Ana papat jinis referensi metode . Kita nggunakake jinis sing nuduhake cara conto saka obyek tartamtu. Ayo miwiti kanthi nemtokake antarmuka sing nemtokake tandha-tandha saka metode sing sampeyan tuju.// Wrapping interface
private interface FunctionPointer {
// Method signatures of pointed method
void methodSignature(int a);
}public void method1(int b) {
System.out.println("Called method1 with integer " + b);
}
public void method2(int v) {
System.out.println("Called method2 with integer " + v);
}
public void method3(int a) {
System.out.println("Called method3 with integer " + a);
}// Create a variable of the interface and assign
// the method references
FunctionPointer pointer1 = this::method1;
FunctionPointer pointer2 = this::method2;
// Call both methods using their "pointer"
pointer1.methodSignature(3);
pointer2.methodSignature(2);
// Reassign and call pointer 1
pointer1 = this::method3;
pointer1.methodSignature(5);
Disebut method1 kanthi integer 3 Disebut method2 kanthi integer 2 Disebut method3 kanthi integer 5
Nggunakake Ekspresi Lambda
Referensi metode bisa ditugasake nggunakake ekspresi lambda.// Create a method reference and assign a methods using a lambda.
FunctionPointer pointer1 =
(a) -> System.out.println("Called pointer1 with int " + a);
FunctionPointer pointer2 =
(b) -> System.out.println("Called pointer2 with int " + b);Array penunjuk fungsi
Fungsi saka macem-macem referensi metode bisa ditiru kanthi nggawe array antarmuka wrapper.// Create an array of "pointers"
FunctionPointer[] functionPointersArray = new FunctionPointer[3];
// Assign methods
functionPointersArray[0] = this::method1;
functionPointersArray[1] = this::method2;
functionPointersArray[2] = this::method3;
// Call methods
functionPointersArray[0].methodSignature(3);
functionPointersArray[1].methodSignature(4);
functionPointersArray[2].methodSignature(5);Fungsi pointer vs panggilan langsung
Yen sampeyan mbandhingake opsi kasebut, nelpon cara langsung meh 5 kaping luwih cepet tinimbang nggunakake referensi metode. Iki kabeh amarga langkah ekstra nelpon ekspresi lambda dibandhingake karo cara sing disimpen. Nanging sampeyan mbokmenawa ora bakal weruh mundhut kinerja ing setahun, mula aja kuwatir.Kesimpulan
Pointer minangka variabel sing ngarah langsung menyang alamat obyek tinimbang nilai. Pointer fungsi langsung nuding alamat fungsi, sing bisa nyuda konsumsi memori. Jawa ora duwe pitunjuk, nanging bisa niru prilaku nggunakake referensi metode utawa ekspresi lambda. Nggunakake referensi metode luwih alon tinimbang nelpon cara langsung, nanging iki ora nyegah panggunaane.indexOf ing Jawa - Carane nemokake indeks string ing Jawa
Sumber: FreeCodeCamp String yaiku sakumpulan karakter sing dilampirake ing tanda kutip ganda. Cara indexOf ngasilake posisi indeks karakter utawa substring sing ditemtokake ing senar. Ing artikel iki, kita bakal sinau babagan sintaks saka macem-macem metode indexOf . Kita uga bakal ndeleng conto sing bakal mbantu sampeyan ngerti lan nggunakake kanthi efektif nggoleki indeks karakter utawa substring ing kode Jawa.
Sintaks metode indexOf
Metode indexOf nduweni metode ing ngisor iki:public int indexOf(int char)
public int indexOf(int char, int fromIndex)
public int indexOf(String str)
public int indexOf(String str, int fromIndex)- char nggantosi siji karakter saben baris.
- fromIndex nemtokake posisi ing ngendi panelusuran kanggo indeks karakter utawa substring kudu diwiwiti. Iki penting nalika sampeyan duwe rong karakter / senar sing duwe nilai sing padha ing senar. Kanthi parameter iki, sampeyan bisa nemtokake cara indexOf ing ngendi arep miwiti.
- str nggambarake substring ing senar.
Cara nggunakake metode indexOf ing Jawa
Ing conto pisanan kita bakal nemokake indeks siji karakter ing senar. Iki bakal mbantu kita ngerti metode public int indexOf(int char) .Contoh metode IndexOf(int Char).
public class Main {
public static void main(String[] args) {
String greetings = "Hello World";
System.out.println(greetings.indexOf("o"));
// 4
}
}Tuladha metode indexOf(int Char, Int fromIndex).
Iki minangka conto sing nerangake metode int indexOf(int char, int fromIndex) :public class Main {
public static void main(String[] args) {
String greetings = "Hello World";
System.out.println(greetings.indexOf("o", 5));
// 7
}
}Tuladha metode Int indexOf(String Str).
Ing conto ing ngisor iki, kita bakal ngerti carane public int indexOf(String str) cara dianggo , sing ngasilake indeks saka substring.public class Main {
public static void main(String[] args) {
String motivation = "Coding can be difficult but don't give up";
System.out.println(motivation.indexOf("be"));
// 11
}
}Tuladha metode indexOf(String Str, Int fromIndex).
Cara pungkasan yaiku public int indexOf(String str, int fromIndex) - padha karo public int indexOf(int char, int fromIndex) method . Iki ngasilake indeks saka posisi sing ditemtokake.public class Main {
public static void main(String[] args) {
String motivation = "The for loop is used for the following";
System.out.println(motivation.indexOf("for", 5));
// 21
}
}public class Main {
public static void main(String[] args) {
String motivation = "The for loop is used for the following";
System.out.println(motivation.indexOf("code"));
// -1
}
}
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