Java Object Type Case cast(Class c, Object o)

Description

An implementation of Class#cast , which is unavailable prior to Java 5.0.

License

BSD License

Exception

Parameter	Description
ClassCastException	If the object cannot be cast to the given type.

Declaration

public static <T> T cast(Class<? extends T> c, Object o) throws ClassCastException 

Method Source Code

//package com.java2s;
/*BEGIN_COPYRIGHT_BLOCK*
    //w  w  w . j av a2s .  c o m
PLT Utilities BSD License
    
Copyright (c) 2007-2010 JavaPLT group at Rice University
All rights reserved.
    
Developed by:   Java Programming Languages Team
        Rice University
        http://www.cs.rice.edu/~javaplt/
    
Redistribution and use in source and binary forms, with or without modification, are permitted 
provided that the following conditions are met:
    
- Redistributions of source code must retain the above copyright notice, this list of conditions 
  and the following disclaimer.
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  conditions and the following disclaimer in the documentation and/or other materials provided 
  with the distribution.
- Neither the name of the JavaPLT group, Rice University, nor the names of the library's 
  contributors may be used to endorse or promote products derived from this software without 
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public class Main {
    /**
     * <p>An implementation of {@link Class#cast}, which is unavailable prior to Java 5.0.  Unlike the
     * Java API method, this version allows a boxed value to be cast to its unboxed equivalent &mdash; for
     * example, {@code ReflectUtil.cast(int.class, 23)} will succeed (see SDN bug 6456930).</p>
     * 
     * <p>The method is only capable of checking that {@code o} is an instance of the class {@code c} &mdash; not 
     * that {@code o} is an instance of type {@code T} (for example, casting with a {@code Class<List<Integer>>} would 
     * only check that {@code o} is a {@code List<?>}, but the return type would by {@code List<Integer>}).
     * Such discrepancies are rare in practice, because class literals ({@code Foo.class}) will only produce classes
     * for which {@code T} is unparameterized or raw.</p>
     * 
     * <p>Following {@code Class.cast()}, a boxed type cannot be cast to its unboxed equivalent, despite the fact
     * that such a cast would be safe.  (From a practical point of view, we would prefer to avoid incurring the
     * overhead of {@link #box} on every cast.)</li>
     * </ul>
     * @throws ClassCastException  If the object cannot be cast to the given type.
     */
    public static <T> T cast(Class<? extends T> c, Object o) throws ClassCastException {
        if (box(c).isInstance(o)) {
            @SuppressWarnings("unchecked")
            T result = (T) o;
            return result;
        } else {
            throw new ClassCastException("Casting to " + c.getName() + " from " + o.getClass().getName());
        }
    }

    /** If {@code c} is a primitive type, return its boxed counterpart; otherwise, return {@code c}. */
    @SuppressWarnings("unchecked")
    public static <T> Class<T> box(Class<T> c) {
        if (c.isPrimitive()) {
            if (c == Boolean.TYPE) {
                return (Class<T>) Boolean.class;
            }
            if (c == Character.TYPE) {
                return (Class<T>) Character.class;
            }
            if (c == Byte.TYPE) {
                return (Class<T>) Byte.class;
            }
            if (c == Short.TYPE) {
                return (Class<T>) Short.class;
            }
            if (c == Integer.TYPE) {
                return (Class<T>) Integer.class;
            }
            if (c == Long.TYPE) {
                return (Class<T>) Long.class;
            }
            if (c == Float.TYPE) {
                return (Class<T>) Float.class;
            }
            if (c == Double.TYPE) {
                return (Class<T>) Double.class;
            }
            if (c == Void.TYPE) {
                return (Class<T>) Void.class;
            }
        }
        return c;
    }

    /**
     * Produce a correctly-typed class corresponding to {@code obj}.  {@code obj.getClass()}, in contrast,
     * returns a {@code Class<?>}.
     */
    @SuppressWarnings("unchecked")
    public static <T> Class<? extends T> getClass(T obj) {
        return (Class<? extends T>) obj.getClass();
    }
}

Related

1. cast(B b0, Class cls)
2. cast(byte b)
3. cast(byte[] bytes)
4. cast(Class c)
5. cast(Class clazz, Object o, T def)
6. cast(Class clazz, Object obj)
7. cast(Class clazz, Object object)
8. cast(Class targetClass, Object obj)