Java Field getChar()方法及实例
java.lang.reflect.Field 的 getChar() 方法用于获得char的值,它必须是静态或实例字段类型。这个方法也用来获取另一个原始类型的值,该类型可以通过拓扑转换为char类型。当一个类包含一个静态或实例Char字段,并且我们想获得该字段的值时,我们可以使用这个方法来返回Field的值。
语法
public char getChar(Object obj) throws IllegalArgumentException, IllegalAccessException
参数: 该方法接受一个单参数 obj ,它是要提取char值的对象。
返回值: 该方法返回转换为char类型的字段的值。
异常: 该方法会抛出以下异常。
- IllegalAccessException: 如果Field对象正在执行Java语言的访问控制,而底层字段是不可访问的,就会抛出这个异常。IllegalArgumentException: 如果指定的对象不是声明底层字段的类或接口的实例,或者如果字段值不能通过拓扑转换为char类型,就会抛出这个异常。NullPointerException: 如果指定的对象是空的,并且该字段是一个实例字段,就会抛出这个异常。ExceptionInitializerError: 如果该方法引发的初始化失败,则抛出该异常。
以下程序说明了getChar()方法:
程序1 :
// Java program to demonstrate the above method import java.lang.reflect.Field; public class GFG { public static void main(String[] args) throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException { // Create the User class object User user = new User(); // Get the identificationChar field object Field field = User.class.getField("identificationChar"); // Apply getChar Method on User Object // to get the value of identificationChar field char value = field.getChar(user); // print result System.out.println("Value of Char Field" + " identificationChar is " + value); // Now Get the selectionChar field object field = User.class.getField("selectionChar"); // Apply getChar Method on User Object // to get the value of selectionChar field value = field.getChar(user); // print result System.out.println("Value of Char Field" + " selectionChar is " + value); }} // sample User classclass User { // static char values public static char identificationChar = 'E'; public static char selectionChar = 'A'; public static String name = "Aman"; // getter and setter methods public static char getIdentificationChar() { return identificationChar; } public static void setIdentificationChar(char identificationChar) { User.identificationChar = identificationChar; } public static char getSelectionChar() { return selectionChar; } public static void setSelectionChar(char selectionChar) { User.selectionChar = selectionChar; } public static String getName() { return name; } public static void setName(String name) { User.name = name; }}
输出:
Value of Char Field identificationChar is EValue of Char Field selectionChar is A
程序2
// Java program to demonstrate the above method import java.lang.reflect.Field; public class GFG { public static void main(String[] args) throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException { // Create the Alphabets class object Alphabets alphabet = new Alphabets(); // Get the value field object Field field = Alphabets.class.getField("value"); // Apply getChar Method on field Object // to get the value of value field char value = field.getChar(alphabet); // print result System.out.println("Value: " + value); } // Alphabets class static class Alphabets { // char field public static char value = 'Q'; // getter and setter methods public static char getValue() { return value; } public static void setValue(char value) { Alphabets.value = value; } }}输出:
Value: Q
参考文献 : https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Field.html#getChar-java.lang.Object-
