/**

* @author Rollen-Holt 使用泛型

*/

class hello {

hello(){

}

public T getName(){

return name;

}

public void setName(T name){

this.name = name;

}

public V getAge(){

return age;

}

public void setAge(V age){

this.age = age;

}

private T name;

private V age;

public static void main(String[] args){

hello he = new hello();

he.setAge(10);

he.setName("Rollen Holt");

System.out.println(he.getName() + " " + he.getAge());

}

}

/**

* @author Rollen-Holt 泛型类的构造方法定义

*/

class hello {

hello(T name, V age){

this.age = age;

this.name = name;

}

public T getName(){

return name;

}

public V getAge(){

return age;

}

private T name;

private V age;

public static void main(String[] args){

hello he=new hello("Rollen",12);

System.out.println(he.getName()+" "+he.getAge());

}

}

/**

* @author Rollen-Holt 使用通配符

*/

class info {

info(T name){

this.name = name;

}

private T name;

}

class hello{

public static void function(info> temp){

System.out.println("内容： "+temp);

}

public static void main(String[] args){

info demo=new info("Rollen");

function(demo);

}

}

/**

* @author Rollen-Holt 泛型上限

*/

class info{

info(T age){

this.age=age;

}

private T age;

}

class hello{

public static void function(info extends Number> temp){

System.out.println("内容"+ temp);

}

public static void main(String[] args){

info demo=new info(1);

function(demo);

}

}

/**

* @author Rollen-Holt 泛型下限

*/

class info{

info(T age){

this.age=age;

}

private T age;

}

class hello{

public static void function(info super String> temp){

System.out.println("内容"+ temp);

}

public static void main(String[] args){

// 此处只能使用String 或者Object

info demo=new info("Rollen");

function(demo);

}

}

/**

* @author Rollen-Holt 泛型和子类继承的限制

*/

class info{

}

class hello{

public static void main(String[] args){

info demo1=new info();

info demo2=new info();

//demo2=demo1; 此处错误

}

}

/**

* 上面的例子说明，一个类的子类可以通过多态性被其父类实例化

* 但是在泛型操作中，子类的泛型类型是无法被其父类的泛型类型实例化的。

*/

如果允许上面的条语句的话，会出现：

Exception in thread "main" java.lang.Error: Unresolved compilation problem:

Type mismatch: cannot convert from info to info

at hello.main(hello.java:12)

泛型接口的两种实现：

/**

* @author Rollen-Holt 泛型接口的实现1

*/

interface info {

public void say();

}

// 直接在子类之后声明泛型

class hello implements info{

public static void main(String[] args){

info demo = new hello();

demo.say();

}

public void say(){

System.out.println("hello");

}

}

/**

* @author Rollen-Holt 泛型接口的实现2

*/

interface info {

public void say();

}

// 在子类实现的接口中明确给出泛型类型

class hello implements info{

public static void main(String[] args){

info demo = new hello();

demo.say();

}

public void say(){

System.out.println("hello");

}

}

/**

* @author Rollen-Holt 使用泛型通一传入参数的类型

*/

class info {

private T var;

public T getVar(){

return var;

}

public void setVar(T var){

this.var = var;

}

public String toString(){

return this.var.toString();

}

}

class hello{

public static void main(String[] args){

info demo1=new info();

info demo2=new info();

demo1.setVar("Rollen");

demo2.setVar("Holt");

printAdd(demo1, demo2);

}

// 此处传递的都是同一个String类型的

public static void printAdd(info demo1, info demo2){

System.out.println(demo1.getVar()+""+demo2.getVar());

}

}

否则的话如下所示：出现错误：

/**

* @author Rollen-Holt 使用泛型通一传入参数的类型

*/

class info {

private T var;

public T getVar(){

return var;

}

public void setVar(T var){

this.var = var;

}

public String toString(){

return this.var.toString();

}

}

class hello{

public static void main(String[] args){

info demo1=new info();

info demo2=new info();

demo1.setVar("Rollen");

demo2.setVar(30);

//此处调用错误

printAdd(demo1, demo2);

}

// 此处传递的都是同一个String类型的

public static void printAdd(info demo1, info demo2){

System.out.println(demo1.getVar()+""+demo2.getVar());

}

}

Exception in thread "main" java.lang.Error: Unresolved compilation problem:

The method printAdd(info, info) in the type hello is not applicable for the arguments (info, info)

at hello.main(hello.java:26)