泛型

代码1

package com.atguigu.day16;
/*
泛型:类型化参数  实参和形参

泛型的好处:
1.可以节约代码
2.可以让代码的可读性更强

* */
public class Demo2 {
    public static void main(String[] args) {
        Pig<String> pig1 = new Pig<>("佩琪","very good");
        Pig<Double> pig2 = new Pig<>("乔治",100.0);
        Pig<Integer> pig3 = new Pig<>("特洛伊",99);
        System.out.println(pig1);//Pig{name='佩琪', score=very good}
        System.out.println(pig2);//Pig{name='乔治', score=100.0}
        System.out.println(pig3);//Pig{name='特洛伊', score=99}

    }
}


class Pig<T>{
    String name;
    T score;

    public Pig() {
    }

    public Pig(String name, T score) {
        this.name = name;
        this.score = score;
    }

    @Override
    public String toString() {
        return "Pig{" +
                "name='" + name + '\'' +
                ", score=" + score +
                '}';
    }
}

代码2

package com.atguigu.day16;
/*
T extends Number & Comparable<T>
T既是Number的孩子，也是Comparable的孩子,指定了T的上限，类型范围不能超过父类
* */
import java.math.BigDecimal;

public class Demo3 {
    public static void main(String[] args) {
        Integer i;
        Double d;
        BigDecimal b;
        SumTools<Integer> sumTools = new SumTools<>(1,5);
        Integer sumValue = sumTools.getSum();
        System.out.println(sumValue);//6

        BigDecimal b1 = new BigDecimal(10.1);
        BigDecimal b2 = new BigDecimal(20.1);
        SumTools<BigDecimal> sumTools1= new SumTools<>(b1,b2);
        BigDecimal b3 = sumTools1.getSum();
        System.out.println(b3);//30.2000000000000010658141036401502788066864013671875
    }
}


class SumTools<T extends Number & Comparable<T>>{
    private T t1;
    private T t2;

    public SumTools(T t1, T t2) {
        this.t1 = t1;
        this.t2 = t2;
    }

    public T getSum(){
        if (t1 instanceof Integer && t2 instanceof Integer){
            Integer values = Integer.valueOf((Integer)t1+(Integer)t2);
            return (T) values;
        }else if (t1 instanceof BigDecimal){
            BigDecimal b1 = (BigDecimal)t1;
            BigDecimal b2 = (BigDecimal)t2;
            BigDecimal values = b1.add(b2);
            return (T) values;
        }
        throw  new UnsupportedOperationException("类型不对");
    }
}

代码3

//泛型方法
public class MyArrays {
    public static <T extends  Comparable> void sort(T[] arr){
        for (int i = 0; i < arr.length-1; i++) {
            for (int j = 0; j < arr.length-i-1; j++) {
                if (arr[j].compareTo(arr[j+1])>0){
                    T t = arr[j];
                    arr[j]=arr[j+1];
                    arr[j+1]=t;
                }
            }

        }
    }

}

import java.util.Arrays;

public class Demo4 {
    public static void main(String[] args) {
        MyArrays myArrays = new MyArrays();
        Dog dog1 = new Dog("哮天",12);
        Dog dog2 = new Dog("大黄",10);
        Dog dog3 = new Dog("小黑",11);
        Dog[] dogsList = {dog1,dog2,dog3};
        myArrays.sort(dogsList);
        System.out.println(Arrays.toString(dogsList));
//[Dog{name='大黄', age=10}, Dog{name='小黑', age=11}, Dog{name='哮天', age=12}]
    }
}


class Dog implements Comparable{
    String name;
    int age;

    public Dog() {
    }

    public Dog(String name, int age) {
        this.name = name;
        this.age = age;
    }

    @Override
    public String toString() {
        return "Dog{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    @Override
    public int compareTo(Object o) {
        Dog dog = (Dog)o;
        return this.age-dog.age;
    }
}

代码4