Java Learning Lesson 32nd (Common Object API)-Basic data type Object wrapper class

Set the base data type (8 types: int). The benefit of encapsulating an object is that it can encapsulate more functions and methods in the object to manipulate the data

A common operation is to use a conversion between a basic data type and a string

Basic data type Object wrapper classes are typically used for conversions between basic types and strings

Basic type-----> string

1. Basic type value + ""

2. Using the valueof (base type value) in the String class

3. Use integer.valueof ();

String--Basic type numeric

1. Use the static method in the wrapper class XXX parsexxx ("XXXX") such as: int parseint ("123")/boolean Parseboolean ("true"), but character has no parse, superfluous

2. If the string is encapsulated by an integer object

A non-static method can be used Intvalue ()

Convert an Integer object to a base type value

(The string is encapsulated into an object before being converted with Xxxvalue)

public class Main {public static void main (string[] args) {/* * Basic Data type wrapper class * To facilitate the base data type value, encapsulate it as an object, define the properties in the object and manipulate the behavior that enriches the data * for The class that describes the object is the basic data type wrapper class *  * byte byte * short Shrot * int Integer * Long long * Double double * Char Character * Boolean Bo Olean *  */int num; System.out.println (integer.max_value);//int Maximum 2147483647system.out.println (integer.tobinarystring (6));// Convert to binary integer x = new Integer ("4"),//system.out.println (x), int xx = Integer.parseint ("1234");//convert string to int, And the parseint method is static System.out.println (XX), if (Boolean.parseboolean ("true")) {integer Xinteger = new Integer ("123");< Span style= "White-space:pre" ></span>system.out.println (Xinteger.intvalue ());//Convert "123" to int}}

Binary conversion

public class Main {public static void main (string[] args) {/* decimal and other */system.out.println (Integer.tobinarystring (6 );//Binary System.out.println (integer.tooctalstring (10));//octal System.out.println (integer.tohexstring (20));// Hex System.out.println (integer.tostring (50, 4));//50 in the representation of the binary/* other  decimal */system.out.println ( Integer.parseint ("110", 2));//110 is considered a binary representation and converted to a decimal System.out.println (Integer.parseint ("3C", 16));}}

Automatic packing and unpacking

public class Main {public static void main (string[] args) {integer a = new Integer ("3"); integer b = new Integer (3); System.out.println (A = = B);//Two new addresses must be different System.out.println (A.equals (b));//equals compares content System.out.println ( A.compareto (b)); int num = 5;num++;integer Xinteger = 5;//xinteger = new Integer (5), auto boxing Xinteger++;//xinteger = Xinteg ER + 1   actual operation   Xinteger = new Integer (Xinteger.intvalue () +1)//Note exception// After JDK1.5, automatic boxing, if the boxing is a byte, then the data will be shared, will not re-open space Integer x = 128;integer y = 128; SYSTEM.OUT.PRINTLN (x = = y);//128 before true,128 and 128 is falseSystem.out.println (X.equals (y));//true}}

Practice:

Import java.util.arrays;/* * Sort the values in a string from small to large * "123 2 5 652 7-3 4 456 456 489" */public class Main {private static  Final String Sps_sigal = "";//ctrl+shift+x lowercase to uppercase, uppercase to lowercase +ypublic static void main (string[] args) {String str = "123 2 5 652 7-3 4 456 456 12 489 "; string[] arr = StringToArray (str); int aa[] = Stringtoint (arr); sort (aa); StringBuilder string = inttostring (AA); show (string);} public static StringBuilder inttostring (int[] arr) {StringBuilder SB = new StringBuilder (), for (int i = 0; i < Arr.leng Th i++) {if (i = = arr.length-1) sb.append (Arr[i]); Elsesb.append (Arr[i] + ",");} return SB;} public static int[] Stringtoint (string[] arr) {int aa[] = new Int[arr.length];for (int i = 0; i < arr.length; i++) {aa[ I] = Integer.parseint (Arr[i]);} return AA;} public static string[] StringToArray (String str) {string[] arr = Str.split (Sps_sigal); return arr;}  public static void sort (int[] arr) {arrays.sort (arr);//Arrays class is provided with the Sort method/* * for (int i = 0;i<arr.length-1;i++) {for (int j = * 0;j<arr.length-1-i;j++) {if (Arr[j] > Arr[j+1]) swap (arr,j,j+1);}} */}public static void Swap (int[] arr, int i, int j) {int t = arr[i];arr[i] = arr[j];arr[j] = t;} public static void Show (StringBuilder string) {System.out.println (string);}}

Java Learning Lesson 32nd (Common Object API)-Basic data type Object wrapper class