java advance class
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Java Advance Class
Imam F Rozi
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Legal Identifier Boleh diawali dengan karakter huruf, $
atau _ dan tidak boleh selainnyatermasuk diawali dengan angka.
Setelah karakter pertama boleh diikutioleh kombinasi karakter apapun Tidak ada batasan panjang karakter Tidak boleh pakai Java Keyword utk
identifier Case Sensitive
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Suns Java Code Convention Class dan Interface
Harus diawali dengan huruf besar Jika namanya terdiri dari 2 atau lebih kata, maka
tiap kata diawali dengan huruf besar Contoh: Pegawai, BangunDatar, PrintWriter,
Seriallizable Method
Huruf pertama diawali dengan huruf kecil
Jika terdiiri dai 2 kata atau lebih, huruf dari katapertama huruf kecil, dan hruf pertama kataselanjutnya diawali dengan huruf besar
Contoh: printInfoPegawai
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JavaBeans Standard JavaBeans merupakan klas dalam Java
yang memiliki atribut. Atribut tsb biasanya memiliki modifier
akses Private. Karena atributnya Private, satu2nya
cara untuk mengaksesnya adalahdengan membuat method dgmodifier akses public.
Method tsb disebut GETTER danSETTER
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JavaBeans Standard
GETTER : method untukmendapatkan/mengambil nilai atributdari klas
SETTER : method untuk memberikannilai kepada atribut dari suatu klas.
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JavaBeans Standard
Aturan penamaan dalam JavaBeans: Jika tipe data atribut selain boolean,
maka nama method getter harus diawalidengan get. Misal atribut gaji getGaji(). Tipe dari getter methodmenyesuaikan dengan tipedata dariatributnya.
Jika tipe data atributnya boolean, makaawalan getter bisa get atau is. Misal:atribut oke tipe data boolean getOke() atau isOke().
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JavaBeans Standard Untuk setter method, diawali dengan set
dan diikuti dengan nama atribut. Misalatribut gaji setGaji(); Tipe settermethod selalu VOID
Getter dan setter harus memiliki modifierakses PUBLIC
Getter tidak punya argumen fungsi Setter memiliki argumen fungsi dengan
tipe data argumen sesuai dengan tipedata atributnya. Misal : atribut double gaji
public void setGaji(double gj).
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Valid JavaBeans Example
public void setMyValue(int v) public int getMyValue()
public boolean isMyStatus()
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Invalid JavaBeans Example
void setCustomerName(String s) //must be public
public void modifyMyValue(int v) //can't use 'modify'
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Paket java.lang Kompiler java otomatis mengimport
seluruh klas dalam paket java.lang kesetiap file program
Klas terpenting yang ada dalam paketini : Object Math Wrapper Class String StringBuffer
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Klas Object Klas Object merupakan klas paling atas atau
akar dari semua klas Java Deklarasi klas tanpa extends Object, secara
implisit pasti ditambahkan extends Object
public class Empolyee(){} Sama dengan Public class Empoyee extends Object(){}
Method yang dimiliki: wait() notify() notifyAll() equals() toString()
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Equals() Method public boolean equals(Object object)
Untuk class Object: Fungsi method equals() sama dengan
operator ==. Yaitu untuk membandingkan reference nya.
Override equals() so that it performs auseful comparison.
Object reference comparison if (d1 == d2)
Relevant instance variables comparison if (d1.equals(d2))
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Contoh
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Contoh
MyDate dt1 = new MyDate(1,2,2000);MyDate dt2 = new myDate(1,2,2000);if (dt1==dt2) System.out.println (sama ); else System.out.println (beda ); if (dt1.equals(dt2))
System.out.println (sama ); else
System.out.println (beda );
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Contoh
Override method equals dari kasMyDate agar lebih berguna
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Method toString()
Menghasilkan representasi string dari stateobject
Menampilkan nama kelas object diikutioleh kode hash
Hash code merupakan tanda unik berupainteger diberikan oleh Java pada object
Override method toString() agar lebihberguna
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String Class
Memiliki beberapa konstruktor. Common string constructors:
String s1 = new String(immutable); String s1 = immutable;
Java mempunyai media penyimpananliteral string yang yang disebut pool.
Jika suatu literal string sudah ada dipool, Java tidak akan membuat copylagi.
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String POOL
Kedua potongan program diatas OK Contoh pertama membandingkan contentnya. Contoh kedua membandingkan referencesnya.
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== dan equals() utk String
Method equals() membandingkancontent-nya
== membandingkan alamatnya
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Contoh
Variabel java1 dieksekusi pada saatruntime
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String method char charAt(int index): Returns the indexed
character of a string, where the index of the initialcharacter is 0.
String concat(String addThis): Returns a new stringconsisting of the old string followed by addThis.
int compareTo(String otherString): Performs a lexicalcomparison; returns an int that is less than 0 if thecurrent string is less than otherString, equal to 0 ifthe strings are identical, and greater than 0 if thecurrent string is greater than otherString.
boolean endsWith(String suffix): Returns true if thecurrent string ends with suffix; otherwise returnsfalse
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String method boolean equals(Object ob): Returns true if ob
instanceof String and the string encapsulated by obmatches the string encapsulated by the executingobject.
boolean equalsIgnoreCase(String s): Creates a new
string with the same value as the executing object,but in lower case. int indexOf(int ch): Returns the index within the
current string of the first occurrence of ch.Alternative forms return the index of a string andbegin searching from a specified offset.
int lastIndexOf(int ch): Returns the index within thecurrent string of the last occurrence of ch. Alternativeforms return the index of a string and end searchingat a specified offset from the end of the string
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String method int length(): Returns the number of characters in the
current string. String replace(char oldChar, char newChar): Returns a
new string, generated by replacing every occurrenceof oldChar with newChar.
boolean startsWith(String prefix): Returns true if thecurrent string begins with prefix; otherwise returnsfalse. Alternate forms begin searching from aspecified offset.
String substring(int startIndex): Returns the substring,beginning at startIndex of the current string andextending to the end of the current string. Analternate form specifies starting and ending offsets.
String toLowerCase(): Creates a new string with thesame value as the executing object, but in lower case
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StringBuffer Class represents a string that can be
dynamically modified. Constructors:
StringBuffer(): Constructs an empty stringbuffer StringBuffer(int capacity): Constructs an
empty string buffer with the specified
initial capacity StringBuffer(String initialString): Constructsa string buffer that initially contains thespecified string
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StringBuffer Method StringBuffer append(String str): Appends str to the current string
buffer. Alternative forms support appending primitives andcharacter arrays; these are converted to strings beforeappending.
StringBuffer append(Object obj): Calls toString() on obj andappends the result to the current string buffer.
StringBuffer insert(int offset, String str): Inserts str into thecurrent string buffer at position offset. There are numerousalternative forms.
StringBuffer reverse(): Reverses the characters of the currentstring buffer.
StringBuffer setCharAt(int offset, char newChar): Replaces thecharacter at position offset with newChar.
StringBuffer setLength(int newLength): Sets the length of thestring buffer to newLength. If newLength is less than the currentlength, the string is truncated. If newLength is greater than thecurrent length, the string is padded with null characters
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Modifying StringBuffer
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String Concatenation the Easy Way concat() method of the String class append() method of the StringBuffer
class
+ operator. Example: String Concatenation: a + b + c
Java compiler treats as: newStringBuffer().append(a).append(b).append(c).toString();
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Math Class
a collection of methods and twoconstants that support mathematicalcomputation.
Two constans: E dan PI is final, so you cannot extend it. constructor is private, so you cannot
create an instance. the methods and constants are static
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Maths method
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Maths method
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Wrapper Class
is simply a class that encapsulatesa single and immutable value.
Integer class wraps up an intvalue,
Float class wraps up a float value.
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Primitive and Wrapper
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equals() dan == pada wrapperclass
Method equals() membandingkancontent-nya
== membandingkan alamatnya
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Contoh equals() dan == pada wrapper
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Retrieval Method public byte byteValue() public short shortValue() public int intValue() public long longValue() public float floatValue() public double doubleValue() public boolean booleanValue() public char charValue()
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Kesimpulan Wrapper Class Tiap tipe data primitif mempunyai
korespondensi dengan satu tipe wrapperclass.
Semua tipe wrapper class dapat dibuat
dari tipe data primitifnya Wrapped values can be tested for equality
with the equals() method. All six numeric wrapper types support all
six numeric XXXValue() methods. Wrapped values can be extracted with
various XXXValue() methods. Wrapped values cannot be modified
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