■getFields()、getDeclaredFields()、getField() 和 getDeclaredField()的用法
1 package reflect.field;
2
3 import java.lang.reflect.Constructor;
4 import java.lang.reflect.Field;
5 import java.lang.reflect.InvocationTargetException;
6 import java.lang.reflect.Method;
7
8 public class FieldMethod {
9
10 public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, SecurityException, NoSuchMethodException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
11 Class<?> personClass = Class.forName("reflect.Person");
12
13 Constructor<?> constructor = personClass.getDeclaredConstructor(String.class, int.class, double.class, String.class);
14 Object p = constructor.newInstance("周娟娟", 23, 80, "14计科1班");
15 System.out.println(p.toString());
16
17
18 // 该方法只能获取到公有的字段(属性)
19 Field[] fields = personClass.getFields();
20 for (Field field : fields) {
21 // System.out.println(field);
22 }
23
24 // 该方法能获取到公有的、私有的、受保护的字段
25 Field[] declaredFields = personClass.getDeclaredFields();
26 for (Field field : declaredFields) {
27 // System.out.println(field);
28 }
29
30 // 该方法只能获取到公有的字段，若传入的是私有或受保护的则会报错NoSuchFieldException
31 Field nameFieldPublic = personClass.getField("className");
32
33 nameFieldPublic.set(p, "卓越班");
34 Method getClassName = personClass.getMethod("getClassName");
35 Object className = getClassName.invoke(p);
36 System.out.println(className);
37
38 // 该方法可以获取到公有的、私有的、受保护的属性
39 Field nameFieldPrivate = personClass.getDeclaredField("name");
40
41 nameFieldPrivate.setAccessible(true);
42 // System.out.println(nameFieldPrivate);
43 nameFieldPrivate.set(p, "Jay");
44 System.out.println(p);
45
46 // 获取到私有属性age
47 Field ageFieldPrivate = personClass.getDeclaredField("age");
48 // 忽略修饰符访问检查
49 ageFieldPrivate.setAccessible(true);
50 // 设置age的值，必须指明修改的是哪个对象的属性
51 ageFieldPrivate.set(p, 24);
52 System.out.println(p);
53
54 }
55
56 }
1 package reflect;
2
3 public class Person {
4
5 private String name;
6 private int age;
7 protected double weight;
8 public String className;
9
10 public Person() {
11 }
12
13 private Person(int age) {
14
15 }
16
17 public Person(String name, int age, double weight, String className) {
18 super();
19 this.name = name;
20 this.age = age;
21 this.weight = weight;
22 this.className = className;
23 }
24
25 public double getWeight() {
26 return weight;
27 }
28
29 public void setWeight(double weight) {
30 this.weight = weight;
31 }
32
33 public String getClassName() {
34 return className;
35 }
36
37 public void setClassName(String className) {
38 this.className = className;
39 }
40
41 public String getName() {
42 return name;
43 }
44
45 public void setName(String name) {
46 this.name = name;
47 }
48
49 private int getAge() {
50 return age;
51 }
52
53 public void setAge(int age) {
54 this.age = age;
55 }
56
57 @Override
58 public String toString() {
59 return "Person [name=" + name + ", age=" + age + ", weight=" + weight
60 + ", className=" + className + "]";
61 }
62
63
64
65 }
