Deeply understand Java reflection and unlock a new realm of Java programming

#The theme of "In-depth understanding of Java reflection and unlocking a new realm of Java programming" recommended by php editor Apple is one of the important topics to discuss Java programming technology. By in-depth study of the Java reflection mechanism, developers can master more advanced programming skills and achieve more flexible and efficient code writing and design. The Java reflection mechanism can not only help developers realize functions such as dynamically loading classes and dynamically calling methods, but also expand the application scenarios of the Java language, improve programming levels, and open up a new realm of Java programming.

In order to deeply understand the reflection mechanism, we first need to understand the Java class loading mechanism. When the Javavirtual machine loads a class, it creates a Class object to represent the class. The Class object contains all the information of the class, including class name, method name, field name, modifiers, etc. We can obtain this information through the Class object and perform dynamic operations on the class.

Class<?> clazz = Class.forName("java.lang.String");
System.out.println(clazz.getName()); // 输出：java.lang.String

In the above code, we use the Class.forName() method to load the java.lang.String class and obtain the Class object of the class. Then, we obtain the name of the class using the getName() method of the Class object.

The reflection mechanism can also be used to create and call objects. We can use the newInstance() method of the Class object to create a new object, or we can use the getMethod() method of the Class object to get a method, and then use this method to call the object's method.

Class<?> clazz = Class.forName("java.lang.String");
Object obj = clazz.newInstance();
System.out.println(obj.toString()); // 输出：""

Method method = clazz.getMethod("length");
int length = (int) method.invoke(obj);
System.out.println(length); // 输出：0

In the above code, we first loaded the java.lang.String class, and then created a new String object using the newInstance() method of the Class object. Next, we use the getMethod() method of the Class object to obtain the length() method of the String class, and then use this method to call the length() method of the String object and output the result.

The reflection mechanism can also be used to modify field values. We can use the getField() method of the Class object to obtain a field, and then use the set() method of the field to modify the field value.

Class<?> clazz = Class.forName("java.lang.String");
Field field = clazz.getField("value");
field.set(obj, "Hello World");
System.out.println(obj.toString()); // 输出：Hello World

In the above code, we first loaded the java.lang.String class, and then used the getField() method of the Class object to obtain the value field of the String class. Next, we use the set() method of the field to modify the value of the field and output the result.

The reflection mechanism is a very powerful function that can be used in many different scenarios, such as dynamically creating objects, dynamically calling methods, dynamically modifying field values, etc. Through reflection, we can greatly improve the flexibility of Java programs.

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