如果使用无限制的类型参数，则Java Compiler会将通用类型的类型参数替换为对象。
package com.learnfk;
public class GenericsTester {
public static void main(String[] args) {
Box<Integer> integerBox = new Box<Integer>();
Box<String> stringBox = new Box<String>();
integerBox</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="kwd">new</span><span class="pln"> </span><span class="typ">Integer</span><span class="pun">(</span><span class="lit">10</span><span class="pun">));</span><span class="pln">
stringBox</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="kwd">new</span><span class="pln"> </span><span class="typ">String</span><span class="pun">(</span><span class="str">"Hello World"</span><span class="pun">));</span><span class="pln">
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">printf</span><span class="pun">(</span><span class="str">"Integer Value :%d\n"</span><span class="pun">,</span><span class="pln"> integerBox</span><span class="pun">.</span><span class="kwd">get</span><span class="pun">());</span><span class="pln">
</span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">printf</span><span class="pun">(</span><span class="str">"String Value :%s\n"</span><span class="pun">,</span><span class="pln"> stringBox</span><span class="pun">.</span><span class="kwd">get</span><span class="pun">());</span><span class="pln">
}
}
class Box<T> {
private T t;
public void add(T t) {
this.t = t;
}
public T get() {
return t;
}
}
在这种情况下，java编译器将T用对象类替换，并且在类型擦除之后，编译器将为以下代码生成字节码。
package com.learnfk;
public class GenericsTester {
public static void main(String[] args) {
Box integerBox = new Box();
Box stringBox = new Box();
integerBox.add(new Integer(10));
stringBox.add(new String("Hello World"));
System.out.printf("Integer Value :%d\n", integerBox.get());
System.out.printf("String Value :%s\n", stringBox.get());
}
}
class Box {
private Object t;
public void add(Object t) {
this.t = t;
}
public Object get() {
return t;
}
}
在两种情况下，输出都是相同的-
Integer Value :10 String Value :Hello World
