Java基础知识

一 Java基础知识

1.01 数组

package com.test.testfan;

public class testfan_01_01_数组 {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO 自动生成的方法存根
        
        int[] a = new int[]{33, 33,3, 44};
        System.out.println(a[0]);
        System.out.println(a.length);
        System.out.println(a[a.length-1]);//获取最后位数据
        
        /*for (int i = 0; i < a.length; i++) {
            int j = a[i];
            System.out.println(j);
        }*/
        
        
        int[] b = new int[100];
        b[0] = 1;
        b[1] = 1;
        b[2] = 1;
        b[3] = 1;
        b[4] = 1;
        System.out.println(b.length);
        

    }

}

1.02 集合

package com.test.testfan;

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

public class testfan_01_02_集合 {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		List<String> list = new ArrayList<String>();
		list.add("200");
		String valueString = list.get(0);
		System.out.println(valueString);
		System.out.println(list.size());//类属性
		//System.out.println(list.);//类属性
		
		//通过数组
		for (int i = 0; i < args.length; i++) {
			String string = args[i];
			
		}
		

		List<Integer> list2 = new ArrayList<Integer>();
		list2.add(200);
		int value2 = list2.get(0);

		for (int i = 0; i < args.length; i++) {
			String string = args[i];
			System.out.println(string);

		}

		//通过集合
		for (Iterator iterator = list2.iterator(); iterator.hasNext();) {
			Integer integer = (Integer) iterator.next();
			System.out.println(integer);
		}
		 
		//通过数组
		for (int i = 0; i < args.length; i++) {
			
		}
		//通过迭代器 
		for (Integer integer : list2) {
			System.out.println(integer);
		}
		
		

	}

}

package com.test.testfan;

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

public class testfan_01_02_集合 {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		List<String> list = new ArrayList<String>();
		list.add("200");
		String valueString = list.get(0);
		System.out.println(valueString);
		System.out.println(list.size());//类属性
		//System.out.println(list.);//类属性
		
		//通过数组
		for (int i = 0; i < args.length; i++) {
			String string = args[i];
			
		}
		

		List<Integer> list2 = new ArrayList<Integer>();
		list2.add(200);
		int value2 = list2.get(0);

		for (int i = 0; i < args.length; i++) {
			String string = args[i];
			System.out.println(string);

		}

		//通过集合
		for (Iterator iterator = list2.iterator(); iterator.hasNext();) {
			Integer integer = (Integer) iterator.next();
			System.out.println(integer);
		}
		 
		//通过数组
		for (int i = 0; i < args.length; i++) {
			
		}
		//通过迭代器 
		for (Integer integer : list2) {
			System.out.println(integer);
		}
		
		
		
		// 数组属性使用
		List<Integer> list3 = new ArrayList<Integer>();
		if(!list3.isEmpty()) {
			int list4 = list3.get(0);
			System.out.println(list4);
		}

		list3.add(200);

	}

}

1.03 对象

package com.test.testfan;

public class Person {
	public String name;
	public int age;
	private double money=1000;
	public String sex;
	public double getMoney() {
		return money;
	}
	public void setMoney(double money) {
		this.money = money;
	}
	
	
	

}

package com.test.testfan;

public class testfan_01_03_对象 {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		
		Person p1 = new Person();
		Person p2 = new Person();
		
		p1.name = "zhangsan";
		p1.setMoney(60000.00);
		System.out.println(p1.name);
		System.out.println(p1.getMoney());
		System.out.println(p1);
		
		System.out.println("-------------");
		
		p2.name = "zhangsan9999";
		p2.setMoney(90000.00);
		System.out.println(p2.name);
		System.out.println(p2.getMoney());
		System.out.println(p2);

	}

}

1.04 继承

package com.test.testfan;

public class Person {
	//成员属性
	public String name;
	public int age;
	private double money=1000;
	public String sex;
	
	
	//成员方法
	public double getMoney() {
		return money;
	}
	public void setMoney(double money) {
		this.money = money;
	}
	
	
	

}

package com.test.testfan;

public class Student  extends Person{

	@Override
	public double getMoney() {
		// TODO 自动生成的方法存根
		//return super.getMoney();
		return 9000.00;
	}

	
}

package com.test.testfan;

public class testfan_01_04_继承 {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		
		Person p1 = new Student();
		
		p1.name = "zhangsan";
		p1.setMoney(60000.00);
		System.out.println(p1.name);
		System.out.println(p1.getMoney());
		System.out.println(p1);
		
		
	}

}

1 父类私有成员属性不进行继承

2 继承后方法进行重写继承类 object类　　

1.05 Equal_ToString

Ctrl+t 查看类间的继承关系
接口不进行实现不可new
抽象类部分实现不可new

数组
ArrayList 线性结构连续空间
LinkLIst 链表结构

集合

package com.test.testfan;

public class Person {
	//成员属性
	public String name;
	public int age;
	private double money=1000;
	public String sex;
	
	
	//成员方法
	public double getMoney() {
		return money;
	}
	public void setMoney(double money) {
		this.money = money;
	}
	/* （非 Javadoc）
	 * @see java.lang.Object#hashCode()
	 */

	
	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + ", money=" + money + ", sex=" + sex + "]";
	}
	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		long temp;
		temp = Double.doubleToLongBits(money);
		result = prime * result + (int) (temp ^ (temp >>> 32));
		return result;
	}
	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Person other = (Person) obj;
		if (Double.doubleToLongBits(money) != Double.doubleToLongBits(other.money))
			return false;
		return true;
	}
	
	
	
	

	
	
	
	
	

}

package com.test.testfan;

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

public class testfan_01_04_Equal_ToString {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		
		Person p1 = new Person();
		Person p2 = new Person();
		
		p1.name = "zhangsan";
		p1.setMoney(90000.00);
		System.out.println(p1.name);
		System.out.println(p1.getMoney());
		System.out.println(p1); //tostring 默认输出的是地址
		
		System.out.println("-------------");
		
		p2.name = "zhangsan9999";
		p2.setMoney(90000.00);
		System.out.println(p2.name);
		System.out.println(p2.getMoney());
		System.out.println(p2);
		
		
		System.out.println(p2==p1); //地址比较
		System.out.println(p2.equals(p1)); //值比较
		List<Person> list9 = new ArrayList<Person>();
		List<Object> list10 = new ArrayList<Object>();
		
	}

}

1.06 集合1

Collection List ArrayList 数组
LinkedList
Set HashSet 集合去重
　　　　TreeSet

Map HashMap
　　TreeMap

package com.test.testfan;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public class testfan_01_05_数组 {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		
		
		// 数组
		List<String> list = new ArrayList<String>(); //线性
		list.add("1");
		list.add("1");
		list.add("3");
		System.out.println(list.size());
		List<String> list2 = new LinkedList<String>(); //分块存放

		
		// 集合 去重
		Set<String> set = new HashSet<String>();
		set.add("1");
		set.add("1");
		set.add("3");
		System.out.println(set.size());
		
		// 集合 排序
		Set<String> set2 = new TreeSet<String>();
		set2.add("1");
		set2.add("1");
		set2.add("3");
		set2.add("9");
		System.out.println(set2.size());
		for (String string : set2) {
			System.out.println(string);
		}
		
	}

}

1.07 集合2

package com_01_testfan_02_basic;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

import sun.security.ssl.KerberosClientKeyExchange;

public class Day01_05_集合2 {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		/**
		 * HashMap和 TreeMap的比较  
		 * HashMap不进行首字母排序；
		 * TreeMap进行首字母排序
		 */
		//HashMap
		Map<String, Object> map = new HashMap<String, Object>();
		map.put("bname", "zhangsan");
		map.put("csex", "男");
		map.put("amoney", 10000);
		Set<String> sets = map.keySet();
		System.out.println(sets.getClass());
		System.out.println(map.containsKey("33333"));
		for (String string : sets) {
			System.out.println("key:" + string + " value:" + map.get(string));
		}
		
		System.out.println();
		//TreeMap
		Map<String, Object> map2 = new TreeMap<String, Object>();
		map2.put("bname", "zhangsan");
		map2.put("csex", "男");
		map2.put("amoney", 10000);
		Set<String> sets2 = map2.keySet();
		System.out.println(sets2.getClass());
		System.out.println(map2.containsKey("33333"));
		for (String string : sets2) {
			System.out.println("key:" + string + " value:" + map2.get(string));
		}

	}

}

posted @ 2019-06-02 14:48 18513757531 阅读(158) 评论(0) 收藏举报

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