Concatenation String ing Jawa

Java String concatenation minangka operasi kanggo nggabungake loro utawa luwih string lan ngasilake sing anyar. Uga, operasi concatenation bisa digunakake kanggo matak jinis kanggo strings. Sampeyan bisa nggabungake senar ing Jawa kanthi rong cara.

metode concat().

Concat () cara appends senar kasebut ing mburi senar diwenehi lan banjur bali lan banjur ngasilake senar anyar kawangun. Manawa kita bisa nggunakake concat () cara kanggo nggabungake telu utawa luwih strings.

Tanda tangan metode concat().

public String concat(String str)

Cara concatenates string str ing mburi string saiki. Tuladhane:

String s1 = “Hello ”; 
s1.concat("World")

ngasilake senar anyar "Hello World".

Concat() conto metode

Ayo concat loro strings sawise initialization sing, banjur concat liyane strings. Lan conto liyane sing menarik: kita bakal nggawe metode sing bakal ngasilake pesen sing beda miturut argumentasi.

public class ConcatTest {

    public static void main(String[] args) {
        //String concat with concat() method 
        String string1 = "I learn ";
        String string2 = "concatenation in Java";
        //here we use concat() method to join the two strings above
        String result = string1.concat(string2);
        System.out.println(result);
        //concat() method to join 4 strings
        String myWebSite = "Code".concat("Gym").concat(".cc").concat("/quest");
        System.out.println(myWebSite); // here we've got  "CodeGym.cc/quest"

        System.out.println(myMessage(true));
        System.out.println(myMessage(false));
    }

    private static String myMessage(boolean b) {   //concat() method with selection statement 
        return "I have".concat(b ? " " : "n't ").concat("got it");
    }

}

Output yaiku: Iku penting kanggo ngerti sing concat () cara ora ngganti senar, nanging nggawe anyar minangka asil gabungan saiki lan liwati minangka parameter. Dadi cara ngasilake obyek String anyar , mula sampeyan bisa nggawe rantai dawa String concat.

Concatenation nggunakake operator overloaded "+" lan "+="

Sampeyan bisa nggunakake rong operator iki kanthi cara sing padha karo nomer. Dheweke kerjane kaya concat() . Ayo concatenate string "Kode" lan string "Gym".

public class StringConcat {
   public static void main(String[] args) {

       String myString = "Code" + "Gym";
       myString+= ".cc";
       System.out.println(myString);
   }
}

Biasane Jawa ora ngidini operasi overloading kanggo kelas panganggo, nanging operator loro iki dianggo minangka overloaded. Sampeyan bisa uga mikir sing nang + operator ndhelikake concat () , nanging nyatane, mekanisme liyane digunakake kene. Yen kita katon ing bytecode program Java, kita bakal weruh sing StringBuilder digawe lan append () cara digunakake. Java Compiler ndeleng operator "+" lan nyadari yen operan minangka senar, dudu jinis primitif. Dadi kerjane kaya concat.

public class StringTest2 {

   public static void main(String[] args) {

       String hello = "hello";
       String world = " world!";

       String helloworld = (new StringBuilder().append(hello).append(world).toString());
       System.out.println(helloworld);
       //this is the same as:
       String result = hello + world;
   }
}

Concat(0) utawa +?

Yen sampeyan perlu kanggo nggabung string mung sapisan, nggunakake concat () cara. Kanggo kabeh kasus liyane, luwih becik nggunakake operator + utawa Stringbuffer / StringBuilder . Uga, operator + digunakake kanggo ngowahi jinis. Yen salah siji saka operan padha, contone, nomer lan nomer loro iku senar, banjur ing metu kita bakal njaluk senar. Tuladha:

public class StringConcat {
   public static void main(String[] args) {
       int myInt = 5;
       String myString = " days";

       System.out.println(myInt + myString);
       boolean b = (myInt + myString) instanceof String;
       System.out.println(b);
   }
}

Kita nggunakake instanceof kanggo mriksa yen (myInt + myString) a String. Mangkene output saka program iki: Wigati uga sing + operator lan concat () bisa beda yen salah siji saka strings null. Yen salah siji operan nalika nggunakake operator + utawa += mung siji - string, banjur, kaya sing wis kasebut, konversi jinis kedadeyan. Padha ditrapake kanggo null. Kita bakal entuk string anyar:

public class StringConcat {
   public static void main(String[] args) {

       String myString = "book ";
       System.out.println(myString + null);
       System.out.println((myString + null) instanceof String);
   }
}

Output yaiku: Yen kita nggunakake cara concat () kanggo operasi sing padha, kita bakal entuk NullPointerException .

public class StringConcat {
   public static void main(String[] args) {

       String myString = "book ";
       System.out.println(myString.concat(null));

   }
}

Output yaiku: