Nogle gange er vi nødt til at kontrollere datatypen for en variabel for at beregne data, fordi vi kan udføre den logiske operation med den samme type variable. For at kontrollere datatypen bruger vi metoden getClass() og getSimpleName() til at få henholdsvis klasse og dens navn. I dette afsnit vil vi diskutere hvordan man kontrollerer datatype i Java?

Lad os implementere koden til at få datatyper af variablerne. Vi tager først input fra brugeren, og derefter finder vi datatypen for de variable, som brugerinput vil blive lagret i.

CheckDataTypeExample.java

 import java.util.*; // create class CheckDataTypeExample to check the datatype of the variable public class CheckDataTypeExample { // main() method start public static void main(String args[]) { // declare variables int intData; char charData; // create Scanner class object to take input from user Scanner sc = new Scanner(System.in); // take input from the user to initialize variables System.out.println('Enter a String value:'); String str = sc.nextLine(); System.out.println('Enter Integer value:'); intData = sc.nextInt(); System.out.println('Enter Character value:'); charData = sc.next().charAt(0); // close Scanner class object sc.close(); // show datatypes of variables by using getClass() and getSimpleName() methods System.out.println(intData + ' is of type ' + ((Object)intData).getClass().getSimpleName()); System.out.println(charData + ' is of type ' + ((Object)charData).getClass().getSimpleName()); System.out.println(str + ' is of type ' + str.getClass().getSimpleName()); } } 

Produktion:

Nu har vi en speciel metode, dvs. getType() leveret af java.lang.reflect.Field og Character klasser. Lad os forstå getType()-metoden for begge klasser én efter én.

Field.getType()

Det getType() metode til marken klasse bruges til at få den type felt, der er defineret af feltobjektet. Returværdien hjælper os med at identificere feltets type.

Syntaks:

Syntaksen for getType() metoden er som følger:

 public String getType() 

Parameter: Den accepterer intet argument som en parameter.

Vender tilbage: Det returnerer et klasseobjekt, der hjælper os med at identificere feltets type.

Lad os tage et eksempel på metoden getType() og forstå, hvordan den virker:

GetTypeExample1.java

 // import required classes and package if any import java.lang.reflect.Field; // create class GetTypeExample1 to get the type of the Field public class GetTypeExample1 { // main() method start public static void main(String[] args)throws Exception { //get the name field object by using getField() method Field nameField = Student.class.getField('name'); // use getTyoe() method of the Field to get the type of name field Class value = nameField.getType(); // print the type of name field System.out.println('The type of the name field is ' + value); //get the totalMarks field object by using getField() method Field marksField = Student.class.getField('totalMarks'); // use getTyoe() method of the Field to get the type of totalMarks field value = marksField.getType(); // print the type of name field System.out.println('The type of the totalMarks field is ' + value); //get the totalFees field object by using getField() method Field feesField = Student.class.getField('totalFees'); // use getTyoe() method of the Field to get the type of name field value = feesField.getType(); // print the type of the totalFees field System.out.println('The type of the totalFees field is ' + value); } } // create a simple student class class Student { // declare and initialize variables public static String name = 'John'; public static double totalMarks = 380; public static float totalFees = 3413.99f; // getter for student name public static String getName() { return name; } // setter for student name public static void setName(String stdName) { name = stdName; } // getter for totalMarks public static double getTotalMarks() { return totalMarks; } // setter for totalMarks public static void setMarks(double marks) { totalMarks = marks; } // getter for totalFees public static float getTotalFees() { return totalFees; } // setter for totalFees public static void setFees(float fees) { totalFees = fees; } } 

Produktion:

Brug af Field.getType()-metoden

Det getType() metode til Karakter klasse bruges til at få generel kategori af det givne tegn. GetType()-metoden kommer med to variationer baseret på parameteren, dvs. Character.getType(char ch) og Character.getType(int codePoint) .

GetType()-metoden, der tager char som parameter, kan ikke håndtere de supplerende tegn, hvorimod getType()-metoden, der tager en int som parameter, kan håndtere supplerende tegn.

Syntaks:

Det getType() metoden til Karakter klasse har følgende syntaks:

 public static int getType(char ch) public static int getType(int codePoint) 

Parameter: Den første variation af metoden getType() accepterer en parameter af typen char og den anden variation af metoden accepterer en parameter af typen int, dvs. codePoint.

Vender tilbage: Begge metoder returnerer en heltalsværdi, der angiver den generelle karakterkategori.

Lad os tage et eksempel på getType()-metoden og forstå, hvordan den virker:

GetTypeExample2.java

 // import required classes and package if any // create class GetTypeExample2 to get the general category of the given character public class GetTypeExample2 { // main() method start public static void main(String[] args)throws Exception { // use setter to set ch1, ch2 in CharData CharData.setChar1('C'); CharData.setChar2('%'); // use getter to get char1 and char2 char char1 = CharData.getChar1(); char char2 = CharData.getChar2(); // use getType() method of Character class int val1 = Character.getType(char1); int val2 = Character.getType(char2); // print categories of char1 and char2 System.out.println('The category of ' +char1 + ' is '+ val1); System.out.println('The category of ' +char2 + ' is '+ val2); } } // create a simple CharData class class CharData { // declare variables of type char static char ch1, ch2; // getter for ch1 public static char getChar1() { return ch1; } // setter for ch1 public static void setChar1(char ch) { ch1 = ch; } // getter for ch2 public static char getChar2() { return ch2; } // setter for ch2 public static void setChar2(char ch) { ch2 = ch; } } 

Produktion:

GetTypeExample3.java

 // import required classes and package if any import java.lang.reflect.Field; // create class GetTypeExample3 to get the general category of the given character public class GetTypeExample3 { // main() method start public static void main(String[] args)throws Exception { // use setter to set code1, code2 in CodePoint CodePoint.setCodePoint1(0x0037); CodePoint.setCodePoint2(0x016f); // use getter to get code1 and code2 int code1 = CodePoint.getCodePoint1(); int code2 = CodePoint.getCodePoint2(); // use getType() method of Character class int val1 = Character.getType(code1); int val2 = Character.getType(code2); // print categories of char1 and char2 System.out.println('The category of ' +code1+ ' is '+ val1); System.out.println('The category of ' +code2+ ' is '+ val2); } } // create a simple CodePoint class class CodePoint { // declare variables of type int static int codePoint1, codePoint2; // getter for codePoint1 public static int getCodePoint1() { return codePoint1; } // setter for codePoint1 public static void setCodePoint1(int code1) { codePoint1 = code1; } // getter for codePoint2 public static int getCodePoint2() { return codePoint2; } // setter for codePoint2 public static void setCodePoint2(int code2) { codePoint2 = code2; } } 

Produktion: