java 泛型的使用

package com.example.hejingzhou.generaldemo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

Gen<String> gen_1 = new Gen<String>("String");
gen_1.showType();

String str = gen_1.getParameters();
Log.i("MainActivity",str);
gen_1.setParameters("设置完毕");
String str1 = gen_1.getParameters();
Log.i("MainActivity", str1);

Log.i("MainActivity", "----------------------------------------------------");

Gen<Integer> gen_2 = new Gen<Integer>(8888);
gen_2.showType();
int integer = gen_2.getParameters();
Log.i("MainActivity", "" + integer);
gen_2.setParameters(9999);
int int2 = gen_2.getParameters();
Log.i("MainActivity", ""+int2);
}
}

class Gen<T>{
private T parameters;//定义泛型成员变量
public Gen(T parameters){
this.parameters = parameters;
}
public T getParameters(){
return parameters;
}
public void setParameters(T parameters){
this.parameters = parameters;
}
public void showType(){
Log.i("MainActivity","T的实际类型是"+parameters.getClass());
}
}

04-02 10:49:33.386 9219-9219/com.example.hejingzhou.generaldemo I/MainActivity: T的实际类型是class java.lang.String
04-02 10:49:33.386 9219-9219/com.example.hejingzhou.generaldemo I/MainActivity: String
04-02 10:49:33.386 9219-9219/com.example.hejingzhou.generaldemo I/MainActivity: 设置完毕
04-02 10:49:33.386 9219-9219/com.example.hejingzhou.generaldemo I/MainActivity: ----------------------------------------------------
04-02 10:49:33.386 9219-9219/com.example.hejingzhou.generaldemo I/MainActivity: T的实际类型是class java.lang.Integer
04-02 10:49:33.386 9219-9219/com.example.hejingzhou.generaldemo I/MainActivity: 8888
04-02 10:49:33.386 9219-9219/com.example.hejingzhou.generaldemo I/MainActivity: 9999