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Session: Java.lang package

Session: Java.lang package. Wrapper Classes. Boolean ( bao bọc )  boolean Character  char Byte  byte Short  short Integer  int Long  long Float  float Double  double. Boolean Class. f asle và true Constructor: Boolean ( boolean b)

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Session: Java.lang package

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  1. Session: Java.langpackage

  2. Wrapper Classes • Boolean (baobọc) boolean • Character  char • Byte  byte • Short  short • Integer  int • Long  long • Float  float • Double  double

  3. Boolean Class • faslevà true • Constructor: Boolean (boolean b) Vídụ: Boolean b1 = new Boolean (false); Boolean (String s) Vídụ: Boolean b2 = new Boolean ("true");

  4. Boolean Class • Methods (phươngthức) booleangetBoolean(String s) Boolean valueOf(String s) booleanbooleanValue()

  5. Boolean Class

  6. Boolean Class • Vídụ 1: viếtchươngtrình kiểmtra nếu a>b: true ngượclại:false  Gợi ý: booleanb3 = (a > b) ? true : false;

  7. Boolean Class • Vídụ 2: viếtchươngtrìnhxuấttừ 1 đến n nếu n làsốlẻ 1, false nếu n làsốchẳn 2, true • Gợi ý: boolean b; for(….) { if(….) { …. b=false; } else … b=true; }

  8. Boolean Class • Vídụ 3: parse a String to a Boolean object • Gợi ý: dùng methods valueOf()

  9. Vídụ 4: return the string representation of a boolean • Gợi ý: toString()

  10. Vídụ 5: Convert String to Boolean • Gợi ý: Boolean.parseBoolean(string)

  11. Character • Các methods: booleanisDigits(char c): return true (c=digit), false booleanisLetter(char): return true (c=letter), false booleanisLetterOrDigit(char c): …. booleanisLowerCase(char c): …. booleanisUpperCase(char c): … booleanisWhitespace(char c): …. char toLowerCase(char c) char toUpperCase(char c) • Vídụ: “ISCOL1-ISCOL2” - letter: 10 - digit: 2 - symbol: 1 - tong char: 13

  12. Character • Vídụ 1: char is 16 bit type and used to represent Unicode characters. Range of char is 0 to 65,536.

  13. Character • Vídụ 2: char variables behave like integers

  14. Character • Vídụ 3: Kiểmtra char is Upper Case • Gợi ý: char a=‘A’ Dùng methods: IsUpperCasekiểmtra

  15. Character • Vídụ 4: tươngtự vd3, kiểmtra char là lower case

  16. Character • Vídụ 5: Kiểmtra char cólà digit

  17. Character • Vídụ 6: (nângcao) kiểmtramộtchuỗiđócótoànlà digit không • Gợi ý: String a= “1234456”  true String b= “12334f1”  false

  18. Character • Vídụ 7: Count letters in a String • Gợi ý: • String str=“abdfhg12sd” • Intdem • isLetter

  19. Byte • byte is smallest Java integer type (-128 đến 127)

  20. Byte • Vídụ 1: Convert byte to String • Gợi ý: • toString()

  21. Short • short is 16 bit signed type ranges from -32,768 to 32,767.

  22. Short • Min and Max values of datatype short • Gợi ý: • Short.Min_Value • Short.Max_Value

  23. Short • Convert Short to numeric primitive data types

  24. Short • Convert Java String to Short • Gợi ý: Short valueOf(String)     String str = "100";    Short sObj2 = Short.valueOf(str);System.out.println(sObj2);

  25. Short • Use toString method of Short class to convert Short into String. • Gợi ý: String toString() short s = 10;    Short sObj = new Short(s);    String str = sObj.toString();System.out.println(str);

  26. Long • Constructor: • Long(long l) • Long(String str) Vídụ: long l = 10;    Long longObj1 = new Long(l);    Long longObj2 = new Long("5");System.out.println(longObj1);System.out.println(longObj2);

  27. Long • Convert Long to numeric primitive data types example • Gợi ý: Giống short

  28. Long • Xuấtgiátrị min vagiátrị max của long

  29. Long • BT1: Viếtchươngtrìnhkiểmtrasốlớnnhất • Gợi ý: • long a, long b, long c

  30. Long • BT2: Tìmsốnhỏnhất • Gợi ý: • long a, long b, long c

  31. Long • Convert Java String to Long example     String str = "100";    Long lObj2 = Long.valueOf(str);System.out.println(lObj2);

  32. Long • Use toString method of Long class to convert Long into String.  Long lObj = new Long(10);    String str = lObj.toString();System.out.println(str);

  33. Float • Java float is 32 bit single precision type and used when fractional precision calculation is required. • Constructor: • Float (float f) • Float (double d) • Vídụ: float f = 12.3f; System.out.println(f);

  34. Float • Min and Max values of data type float

  35. Float • BT1: so sánh 2 con số • Gợi ý: Cách 1: inti= Float.compare(a, b) Cách 2: int j = a.compareTo(b)

  36. Float • Cách 1: float f1 = 5.5f;float f2 = 5.4f;inti1 = Float.compare(f1, f2);if (i1 > 0) {System.out.println(">");    } else if (i1 < 0) {System.out.println("<");    } else {System.out.println("=");    }

  37. Float • Cách 2: Float fObj1 = new Float(5.5);    Float fObj2 = new Float(5.4);inti2 = fObj1.compareTo(fObj2);if (i2 > 0) {System.out.println(">");    } else if (i2 < 0) {System.out.println("<");    } else {System.out.println("=");    }

  38. Float • Boolean isNaN(): return true (value is NaN), false • NaN: Not a Number • Vídụ: Kiểmtra float f

  39. Float Cách 1 float f = (float) Math.sqrt(-10);booleanb1 = Float.isNaN(f);System.out.println(b1); Cách 2 float f = (float) Math.sqrt(-10);    Float fObj = new Float(f);booleanb2 = fObj.isNaN();System.out.println(b2);

  40. Float • Use toString method of Float class to convert Float into String. • Vídụ: Float fObj = new Float(10.25);    String str = fObj.toString();System.out.println(str);

  41. Other classes in the java.lang package • Math • System • Object • Class • ThreadGroup • Runtime

  42. Math class

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