java--Eight basic data types (common classes)

• Packing and unpacking

1. Boxing: Basic data type to wrapper class
2. Unpacking: Wrapper class to basic data type
3. jdk1.5 (i.e. jdk5.0) versions are available with auto-boxing and auto-unpacking capabilities

• Wrapper classes for basic data types
• For two examples, take a look at

1  Public classDemo01 {2     3      Public Static voidMain (string[] args) {4         5         6         7         inti = 3;//Basic data Types8Integer I1 =NewInteger (i);//Packing class packing9 System.out.println (i);Ten System.out.println (i1); One          A          -         //Turn 100 of the string into a number -String s = "100"; the         //String s = "abc"; Wrong, Java.lang.NumberFormatException . -Integer i2 =NewInteger (s); - System.out.println (i2); -          +          -         inti3 = I1.intvalue ();//Unpacking + System.out.println (i3); A          at          -         //S--> int -         intI4 = Integer.parseint (s);//How to convert a string to a number - System.out.println (I4); -          -          in          -         //automatic boxing and unpacking after JDK 1.5 to         intj = 5; +          -Integer J1 = j;//Automatic Boxing//integer J3 = new Integer (j); the          *         intJ2 = J1;//Automatic Unpacking $         Panax Notoginseng          -         //print maximum and minimum values of type int the System.out.println (integer.max_value); + System.out.println (integer.min_value); A          the          +         //Binary Conversion -         //Decimal Turn hex $System.out.println (integer.tohexstring (1000)); $         //Decimal Turn octal -System.out.println (integer.tooctalstring (9)); -         //Decimal Turn binary theSystem.out.println (Integer.tobinarystring (3)); -         Wuyi          the          -Integer II1 =NewInteger (1234);//heap in-memory fetch WuInteger II2 = 1234;//go to the method area to find -         intII3 = 1234;//II1 Unpacking int About          $System.out.println (II1 = = Ii3);//T -          -         //Although the property values are the same, but the referenced addresses are different, "= =" compares the referenced addresses -System.out.println (II1==II2);//F A          +         //The equals method is overridden in the Integer class, compared to the property value theSystem.out.println (Ii1.equals (II2));//T -          $          the         //byte [ -128-127] the          theByte B1 =-123; theByte B2 =-123; -          inSystem.out.println (B1 = =B2); the System.out.println (B1.equals (B2)); the          About          the          the}

1  Public classDemo02_character {2     3      Public Static voidMain (string[] args) {4         5System.out.println ((int) ' 1 ');6         7         CharC1 = ' A ';8         CharC2 = 49;9System.out.println ("C2 =" +C2);Ten          OneCharacter C3 = C1;//Character C4 = new Character (c1); A          -System.out.println (Character.isdigit (C1));//determines whether a character is a number F -System.out.println (Character.isletter (C1));//determines whether a character is a letter T theSystem.out.println (Character.islowercase (C1));//determine if the lowercase letter F -System.out.println (Character.isuppercase (C1));//determine if an uppercase T -          -System.out.println (character.tolowercase (' C '));//uppercase to lowercase c +System.out.println (Character.touppercase (' a '));//lowercase to uppercase A -          +}

• Similar to the use of byte/short/long/float/double and Integer (int) classes

java--Eight basic data types (common classes)