Java Class. cast method, javaclass. cast Method

Java Class. cast method, javaclass. cast Method
1. Java api

public T cast(Object obj);

Casts an object to the class or interface represented

The general explanation means to replace an object with a class or interface.

2. Sample Code

/** * Created by shengke on 2016/10/22. */class A {    public static void show() {        System.out.println("Class A show() function");    }}class B extends A {    public static void show() {        System.out.println("Class B show() function");    }}public class TestCast {    public static void main(String[] args) {        TestCast cls = new TestCast();        Class c = cls.getClass();        System.out.println(c);        Object obj = new A();        B b1 = new B();        b1.show();        // casts object        A a = new A();        a = A.class.cast(b1);        System.out.println(obj.getClass());        System.out.println(b1.getClass());        System.out.println(a.getClass());    }}

Execution result

class com.scot.effective.genericity.TestCastClass B show() functionclass com.scot.effective.genericity.Aclass com.scot.effective.genericity.Bclass com.scot.effective.genericity.B　　

Core: a = A. class. cast (b1); converting a to B is easy to produce misunderstanding of converting b1 to.

3. Source Code

    /**     * Casts an object to the class or interface represented     * by this {@code Class} object.     *     * @param obj the object to be cast     * @return the object after casting, or null if obj is null     *     * @throws ClassCastException if the object is not     * null and is not assignable to the type T.     *     * @since 1.5     */    public T cast(Object obj) {        if (obj != null && !isInstance(obj))            throw new ClassCastException(cannotCastMsg(obj));        return (T) obj;    }

4. Summary

This method can only convert objects of the current type or its sub-classes, but simply performs a forced conversion.