Java Basic Data Type wrapper class (ix)

wrapper classes (e.g., integer,double, etc.) these classes encapsulate a corresponding base data type value and provide it with a series of operations.

Take the Java.lang.Integer class, for example, to construct the method:

Integer (int value);

Integer (String s);

Common methods:

public static final int max_value: Maximum int type (2^31-1)

public static final int min_value: Smallest int type ( -2^31)

Public long Longvalue (): Returns the Long value of the encapsulated data

Public double Doublevalue (): Returns the double type value of the encapsulated data

public int intvalue (): Returns the int type value of the encapsulated data

public static int parseint (string s) throws NumberFormatException: parses the string into int data and returns the data

public static integer valueOf (string s) throws NumberFormatException: Returns an Integer object in which the encapsulated integer data is represented by the string s.

Package mywrapperclass;

public class Test {

public static void Main (string[] args) {

TODO auto-generated Method Stub

Integer i=new integer (100);

Double D=new double ("123.456");

int J=i.intvalue () +d.intvalue ();

System.out.println ("J:" +j);

Float F=i.floatvalue () +d.floatvalue ();

System.out.println ("F:" +f);

Double pi=double.parsedouble ("3.1415926");

Double r=double.valueof ("2.0"). Doublevalue ();

Double s=pi*r*r;

System.out.println (s);

try{

int K=integer.parseint ("125.0");

}catch (NumberFormatException e) {

SYSTEM.OUT.PRINTLN ("The data format is wrong! ");

}

System.out.println (integer.tobinarystring (2) + "B");

System.out.println (integer.tohexstring (2) + "H");

System.out.println (integer.tooctalstring (2) + "O");

System.out.println (Integer.max_value);

System.out.println (Integer.min_value);

}

}

Writes a method that returns a double-type two-dimensional array in which the elements of the array are obtained by parsing the string parameters. such as the string parameter: "1,2;3,4,5;6,7,8".

Package mywrapperclass;

public class Teststringpractice {

public static void Main (string[] args) {

TODO auto-generated Method Stub

String s= "1,2;3,4,5;6,7,8";

String s1[]=s.split (";");

System.out.println (s1.length);

Double D[][]=new double[s1.length][];

for (int i=0;i<s1.length;i++) {

String temp[]=s1[i].split (",");

System.out.println (temp.length);

Defining a multidimensional array, defining a high dimension, int[][] a=new int[10][], and then defining a low dimension, you must define a low dimension because the memory is not allocated to the low dimension and the null pointer error is reported.

Low dimensional definition mode a[0]=new int[2];

D[i]=new Double[temp.length];

for (int j=0;j<temp.length;j++) {

D[i][j]=double.valueof (Temp[j]). Doublevalue ();

System.out.print (d[i][j]+ "");

}

System.out.println ();

}

}

}

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Java Basic Data Type wrapper class (ix)