java小效能点_2

1、Arrays.asList()方法的使用

    该方法是将数组转化为list；

    该方法不适用于基本数据类型(byte,short,int,long,float,double,boolean);

    该方法将数组与列表链接起来，当更新其中之一时，另一个自动更新;

    不支持add和remove方法，它的长度是不能改变的;

    参考地址：

         http://blog.csdn.net/keketrtr/article/details/47108435

         https://www.cnblogs.com/shanheyongmu/p/6364320.html

2、List的contains()方法

     说明：该方法判断集合list中包含元素b

     语法：list.contains(obj)

package com.wanrong.adminWeb;

import java.util.ArrayList;
import java.util.List;

public class Test1 {
    public static void main(String[] args) {
        List<String> listA = new ArrayList<String>();
        listA.add("111");
        listA.add("222");
        listA.add("333");
        listA.add("444");
        
        System.out.println(listA.contains("222"));
        System.out.println(listA.contains("2221"));
        System.out.println("------------------------------------------------");

        List<Object> listB = new ArrayList<Object>();
        A a1 = new A("11", "男", "你哥1");
        A a2 = new A("12", "男", "你哥2");
        A a3 = new A("13", "男", "你哥3");
        A a4 = new A("14", "男", "你哥4");
        
        B b1 = new B("15", "男", "你哥5");
        listB.add(a1);
        listB.add(a2);
        listB.add(a3);
        System.out.println(listB.contains(a1));
        System.out.println(listB.contains(a2));
        System.out.println(listB.contains(a4));
        System.out.println(listB.contains(b1));
    }
    
    private static class A {
        private String age_1;
        private String sex_1;
        private String name_1;
        
        A(String age_1, String sex_1, String name_1){
            age_1 = age_1;
            sex_1 = sex_1;
            name_1 = name_1;
        }
    }
    
    private static class B {
        private String age_2;
        private String sex_2;
        private String name_2;
        
        B(String age_2, String sex_2, String name_2){
            this.age_2 = age_2;
            this.sex_2 = sex_2;
            this.name_2 = name_2;
        }
    }
}

 输出结果：

true
false
------------------------------------------------
true
true
false
false