泛型：所谓泛型，就是变量的类型参数化。
作用：限制泛型可用类型。
简单的泛型定义使用：
public class GenericFoo<T> {
private T foo;
public void setFoo(T foo){
this.foo = foo;
}
public T getFoo(){
return this.foo;
}
public static void main(String[] args){
//GenericFoo is a raw type, References to generic type GenericFoo<T> should be parameterized.
GenericFoo foo = new GenericFoo();
GenericFoo<String> sFoo = new GenericFoo<String>();
GenericFoo<Integer> iFoo = new GenericFoo<Integer>();
sFoo.setFoo("string foo");
// sFoo.setFoo(11); //这里只能放置String类型的，放置11在编译时就会报错。
iFoo.setFoo(11);
}
}2.定义两个泛型，以及泛型数组的定义使用：
public class GenericFoo2<T,E> {
private T foo1;
private E foo2;
private T[] arrays;
public T getFoo1() {
return foo1;
}
public void setFoo1(T foo1) {
this.foo1 = foo1;
}
public E getFoo2() {
return foo2;
}
public void setFoo2(E foo2) {
this.foo2 = foo2;
}
public T[] getArrays() {
return arrays;
}
public void setArrays(T[] arrays) {
this.arrays = arrays;
}
public static void main(String[] args){
GenericFoo2<String,Boolean> gf = new GenericFoo2<String,Boolean>();
gf.setFoo1("string");
gf.setFoo2(false);
gf.setArrays(new String[]{"aa","bb"});
}
}3.模仿ArrayList实现集合泛型化：
public class GenericCollection<E> {
private Object[] array;
private int index;
public GenericCollection(){
this(10);
}
public GenericCollection(int capacity){
array = new Object[capacity];
}
public void add(E e){
array[index++] = e;
}
public E get(int index){
return (E)array[index];
}
public static void main(String[] args){
GenericCollection<Integer> gc = new GenericCollection<Integer>();
for(int i=0;i<10;i++){
gc.add(i*2);
}
for(int i=0;i<10;i++){
System.out.println(gc.get(i));
}
}
}
