一、一维数组

概念:存放多个数据的容器
声明:数据类型[] 数组名;

注意:

	元素:数组中的数据
	下标/索引:元素在数组中的编号,从0开始
	数组是引用数据类型,一旦初始化后,会在内存中开辟一连串连续的空间
	数组初始化后,长度是不可以改变的,所以数组没有添加或删除的功能

初始化:

	静态初始化:数据由程序员给定,长度由系统自动分配
	动态初始化:长度由程序员给定,数据由系统自动分配
		整数类型数组的默认值:0				int[] is = new int[10];
		浮点数类型数组的默认值:0.0	     double[] ds = new double[10];
		字符类型数组的默认值:' ' 			  char[] cs = new char[10];
		布尔类型数组的默认值:false	 	 boolean[] bs = new boolean[10];
		引用类型数组的默认值:null	 	   String[] ss = new String[10];

静态初始化:一开始就知道数据
静态初始化内存图
在这里插入图片描述

动态初始化:一开始就知道数组长度,不知道具体数据
动态初始化内存图
在这里插入图片描述

public static void main(String[] args){
	//静态初始化1
	//String[] names = new String[]{"麻生希","三上悠亚","水野朝阳","桃谷绘里香","明日花绮罗"};

	//静态初始化2
	//String[] names;
	//names = new String[]{"麻生希","三上悠亚","水野朝阳","桃谷绘里香","明日花绮罗"};

	//静态初始化3
	String[] names = {"麻生希","三上悠亚","水野朝阳","桃谷绘里香","明日花绮罗"};

	//设置指定下标上的元素
	names[2] = "杨晨";

	//获取指定下标上的元素
	String str = names[2];
	System.out.println("获取指定下标上的元素:" + str);

	//获取元素的个数
	int length = names.length;
	System.out.println("获取元素的个数:" + length);
	
	System.out.println("--------------");
	
	//遍历:从头到尾
	
	//for循环
	for(int i = 0;i<names.length;i++){
		System.out.println(names[i]);
	}
	System.out.println("--------------");
	
	//foreach 增强for循环(依次取出数组中的元素,并赋值给name)
	for(String name : names){
		System.out.println(name);
	}
	
	/**
		for vs foreach
			for中可以使用到下标
			foreach中不能使用下标
	*/
	
	//注意:ArrayIndexOutOfBoundsException -- 数组下标越界异常
	//System.out.println(names[5]);
}

数组案例:声明5个数据的int数组,求出最大值(数据自己写)

​	注意:
	​		int为基本数据类型
	​		int[] 为引用数据类型
public static void main(String[] args){
	
	int[] is = {35,86,12,66,45};
	
	int max = is[0];
	
	for(int i = 1;i<is.length;i++){
		if(max < is[i]){
			max = is[i];
		}
	}
	
	System.out.println("最大值为:" + max);	
}

数组的排序

冒泡排序
口诀:

		N个数字来排序
		两两相比小靠前
		外层循环N-1
		内层循环N-1-i

选择自学:选择排序、插入排序

int[] is = {10,55,36,89,35,61,1};

for(int i = 0;i<is.length-1;i++){
	for(int j=0;j<is.length-1-i;j++){
		if(is[j] > is[j+1]){
			int temp = is[j];
			is[j] = is[j+1];
			is[j+1] = temp;
		}
	}
}

for(int num:is){
	System.out.println(num);
}

数组的查找

  1. 顺序查找
int[] is = {10,55,36,89,35,61,1};
int num = 55;
for(int i = 0;i<is.length;i++){
	if(is[i] == num){
		System.out.println("找到了");
	}
}
  1. 二分法查找(前提:先排序再查找)
int[] is = {10,55,36,89,35,61,1};

int num = 55;

//排序
Arrays.sort(is);

int start = 0;
int end = is.length-1;

while(start <= end){
	int mid = (start+end)/2;
	
	if(num > is[mid]){
		start = mid+1;
	}else if(num < is[mid]){
		end = mid-1;
	}else{
		System.out.println("找到了");
		break;
	}
}

数组的复制1

缺点:更改原数组的数据,新数组也会发生改变

String[] names = {"麻生希","爱田奈奈","小峰由衣"};

String[] newNames = names;

names[1] = "杨晨";

for(String str : newNames){
	System.out.println(str);
}

数组的复制2

String[] names = {"麻生希","爱田奈奈","小峰由衣"};

String[] newNames = new String[names.length];

for(int i = 0;i<names.length;i++){
	newNames[i] = names[i];
}

names[1] = "杨晨";

for(String str : newNames){
	System.out.println(str);
}	

数组的扩容

String[] names = {"麻生希","爱田奈奈","小峰由衣"};

String[] newNames = new String[names.length*2];

for(int i = 0;i<names.length;i++){
	newNames[i] = names[i];
}

names = newNames;

for(String str : names){
	System.out.println(str);
}	

数组的删除1

缺点:数组的长度变短了

String[] names = {"麻生希","爱田奈奈","小峰由衣"};//0 1 2

String[] newNames = new String[names.length-1];//0 1

int index = 0;
for(String n : names){
	if(!n.equals("爱田奈奈")){
		newNames[index] = n;
		index++;
	}
}

names = newNames;

for(String n:names){
	System.out.println(n);
}

数组的删除2

String[] names = {"麻生希","爱田奈奈","小峰由衣","水野朝阳","深田咏美"};

for(int i = 1;i<names.length-1;i++){
	names[i] = names[i+1];
}
names[names.length-1] = null;
for(String n:names){
	System.out.println(n);
}

数组参数和返回值

需求:设计一个方法,传入数组,返回最大值和最小值

public static void main(String[] args){
    
	int[] is = {10,55,36,89,35,61,1};
	
	int[] maxMin = getNum(is);
	
	System.out.println("最大值:" + maxMin[0]);
	System.out.println("最小值:" + maxMin[1]);
}

public static int[] getNum(int[] is){
	
	int max = getMax(is);
	int min = getMin(is);
	return new int[]{max,min};
}

public static int getMax(int[] is){
	int max = is[0];
	for(int i = 1;i<is.length;i++){
		if(max < is[i]){
			max = is[i];
		}
	}
	return max;
}

public static int getMin(int[] is){
	int min = is[0];
	for(int i = 1;i<is.length;i++){
		if(min > is[i]){
			min = is[i];
		}
	}
	return min;
}

可变参数

含义:可变参数本质意义就是数组

public static void main(String[] args){
	/**
		可变参数
		
		含义:可变参数本质意义就是数组
	*/
	
	int sum = add(1,2,3);//将实参认为是数组的元素,压入到数组中
	System.out.println("总和为:" + sum);
}

public static int add(int... is){//可变参数就是数组
	int sum = 0;
	for(int num:is){
		sum+=num;
	}
	return sum;
}

//规则:可变参数后不能加其他形参
//public static void method(String str,int... is){}

Arrays工具类

Arrays工具类:Java提供的专门操作数组的类
工具类:该类里的方法都是静态的,直接用类名调用
API:Java提供类的使用说明书

int[] is = {10,55,36,89,35,61,1};

//排序
Arrays.sort(is);//1,10,35,36,55,61,89

//查找(返回值:如果该元素在数组中就返回下标,否则返回 -插入点-1)
int index = Arrays.binarySearch(is,69);
System.out.println("查找的元素下标为:" + index);

//替换 
Arrays.fill(is,888);
Arrays.fill(is,1,4,666);

//把数组转换为字符串
String isStr = Arrays.toString(is);
System.out.println(isStr);

//拷贝1
int[] newIs1 = Arrays.copyOf(is,10);
System.out.println(Arrays.toString(newIs1));

//拷贝2
int[] newIs2 = Arrays.copyOfRange(is,1,4);
System.out.println(Arrays.toString(newIs2));

超简易学生姓名管理系统

package com.dream.test01;
import java.util.Arrays;
import java.util.Scanner;

public class Test01 {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);

		System.out.println("欢迎进入学生管理系统!");
		boolean flag = true;
		String name;
		while (true) {
			System.out.println("请选择功能:");
			System.out.println("1-添加姓名 2-删除姓名 3-修改姓名 4-打印所有学生姓名 886-退出系统");
			int num = scan.nextInt();
			switch (num) {
			case 1:
				System.out.println("请输入要添加的姓名:");
				name = scan.next();
				if (add(name)) {
					System.out.println("添加成功");
				}else {
					System.out.println("添加失败");
				}
				break;
			case 2:
				System.out.println("请输入要删除的姓名:");
				name = scan.next();
				if (delete(name)) {
					System.out.println("删除成功");
				}else {
					System.out.println("删除失败");
				}
				break;
			case 3:
				System.out.println("请输入要修改的名字:");
				name = scan.next();
				System.out.println("请输入修改后的名字:");
				String newName = scan.next();
				if (update(name,newName)) {
					System.out.println("修改成功");
				}else {
					System.out.println("修改失败");
				}
				break;
			case 4:
				printName();
				break;	
			case 886:
				flag = false;
				printName();
				break;	
			default:
				System.out.println("输入有误,请重新输...");
				break;
			}
			scan.close();
		}
		
		
	}
	
	//全局变量
	static String[] names = new String[3];
	static int point = 0;
	//添加姓名
	public static boolean add(String name) {
		//判断姓名合法性
		if (name.length()>8) {
			System.out.println("名字个数不能大于8");
			return false;
		}
		//查询是否有该学生
		if (query(name)!=-1) {
			return false;
		}
		//扩容
		if (point ==names.length) {
			names = Arrays.copyOf(names, names.length+1);
		}
		//添加
		names[point++]=name;
		return true;
	}
	//删除姓名
	public static boolean delete(String name) {
		//判断姓名合法性
		if (name.length()>8) {
			System.out.println("名字个数不能大于8");
			return false;
		}	
		int query =  query(name);
		//查询是否有该学生
		if (query==-1) {
			return false;
		}
		//删除
		for (int i = query; i < point-1; i++) {
			names[i] = names[i+1];
		}
		point--;
		return true;
	}
	//查询姓名
	public static int query(String name) {
		for (int i = 0; i < point; i++) {
			if (names[i].equals(name)) {
				return i;
			}
		}
		return -1;
	}
	//修改姓名
	public static boolean update(String sourceName,String targetName) {
		//查询是否有该学生
		int  query = query(sourceName);
		if ( query==-1) {
			System.out.println("没有该学生");
			return false;
		}
		//判断是否与原名相同
		if (sourceName.equals(targetName)) {
			System.out.println("更改名不能与原名相同!");
			return false;
		}
		//判断姓名合法性
		if (targetName.length()>8) {
			System.out.println("名字个数不能大于8");
			return false;
		}
		//修改名字
		names[query(sourceName)] = targetName;	
		return true;
	}
	//打印全部学生
	public static void printName() {
		for (int i = 0; i < point; i++) {
			System.out.println(names[i]);
		}
	}
}

二维数组

含义:二维数组中,包含了多个一维数组

声明:数据类型[] [] 数组名;

初始化:

静态初始化:数据由程序员给定,长度由系统分配

//静态初始化1
	String[][] names = new String[][]{{"北岛玲","椎名空","刘坤杰"},{"爱田奈奈","北条麻衣","吉泽明步","三上悠亚"}};
		
//静态初始化2
	String[][] names;
	names = new String[][]{{"北岛玲","椎名空","刘坤杰"},{"爱田奈奈","北条麻衣","吉泽明步","三上悠亚"}};

//静态初始化3
	String[][] names = {{"北岛玲","椎名空","刘坤杰"},{"爱田奈奈","北条麻衣","吉泽明步","三上悠亚"}};

动态初始化:长度由程序员给定,数据由系统分配

//动态初始化1
	String[][] names = new String[2][3];//2个一维数组,每个一维数组分别有3个元素
	
//动态初始化2
	String[][] names;
	names = new String[2][3];//2个一维数组,每个一维数组分别有3个元素

基本操作:

//通过下标设置元素
	names[1][2] = "明日花绮罗";
	
//通过下标获取元素
	String n = names[1][2];
	System.out.println(n);
	
//获取长度
	System.out.println("获取二维数组中一维数组的个数:" + names.length);//2
	System.out.println("获取二维数组中第一个一维数组元素的个数:" + names[0].length);//3
	System.out.println("获取二维数组中第二个一维数组元素的个数:" + names[1].length);//4

遍历
遍历思路:先取出二维数组中的一维数组,再取出去一维数组中的元素

//遍历1:for循环
	for (int i = 0; i < names.length; i++) {
		for (int j = 0; j < names[i].length; j++) {
			System.out.println(names[i][j]);
		}
	}
	
//遍历2:增强for循环
	for (String[] ss : names) {
		for (String element : ss) {
			System.out.println(element);
		}
	}

简易五子棋
友情提示:eclipes字体设置为宋体才能正常显示

package com.dream.test;

import java.util.Scanner;

public class Test {

	public static void main(String[] args) {
		
		Scanner scan = new Scanner(System.in);
		
		int length = 20;//棋盘长度
		String[][] goBang = new String[length][length];//棋盘容器
		//坐标的数组
		String[] nums = {"⒈","⒉","⒊","⒋","⒌","⒍","⒎","⒏","⒐","⒑","⒒","⒓","⒔","⒕","⒖","⒗","⒘","⒙","⒚","⒛"};
		//符号
		String add = "╋";
		String black = "■";
		String white = "○";
		
		//初始化棋盘容器里的数据
		for (int i = 0; i < goBang.length; i++) {
			for (int j = 0; j < goBang[i].length; j++) {
				if(j == length-1){//每一行的最后一列
					goBang[i][j] = nums[i];
				}else if(i == length-1){//最后一行
					goBang[i][j] = nums[j];
				}else{
					goBang[i][j] = add;
				}
			}
		}
		
		//打印棋盘
		for (String[] ss : goBang) {
			for (String e : ss) {
				System.out.print(e);
			}
			System.out.println();
		}
		
		//落子
		boolean bool = true;//true-黑子 false-白子
		while(true){
			
			System.out.println("请" + ((bool)?"黑":"白") + "子输入坐标:");
			int x = scan.nextInt()-1;
			int y = scan.nextInt()-1;
			
			//判断坐标是否超出棋盘范围
			if(x < 0 || x > length-2 || y < 0 || y > length-2){
				System.out.println("坐标超出棋盘范围,请重新输入");
				continue;
			}
			
			//判断坐标上是否有棋子
			if(!goBang[y][x].equals(add)){
				System.out.println("坐标上有棋子,请重新输入");
				continue;
			}
			
			//落子
			goBang[y][x] = (bool)?black:white;
			
			//置反
			bool = !bool;
			
			//打印棋盘
			for (String[] ss : goBang) {
				for (String e : ss) {
					System.out.print(e);
				}
				System.out.println();
			}
			
			//判断输赢
			if (xAxis(x, y, goBang, black) || yAxis(x, y, goBang, black) || xyAxis(x, y, goBang, black) || yxAxis(x, y, goBang, black)) {
				System.out.println("恭喜黑子方获胜!");
				break;
			}
			if (xAxis(x, y, goBang, white) || yAxis(x, y, goBang, white) || xyAxis(x, y, goBang, white) || yxAxis(x, y, goBang, white)) {
				System.out.println("恭喜白子方获胜!");
				break;
			}
		}
	
	}




	//水平方向
	public static boolean xAxis(int x,int y,String[][] goBang,String fh){
		int length = 20;
		int count = 1;
		for (int i = x+1; i < length; i++) {
			if (goBang[y][i].equals(fh)) {
				count++;
			}else {
				break;
			}
		}
		for (int i = x-1; i >= 0; i--) {
			if (goBang[y][i].equals(fh)) {
				count++;
			}else {
				break;
			}
		}
		//System.out.println(count);
		if (count >= 5) {
			return true;
		}
		return false;
	}
	//垂直方向
	public static boolean yAxis(int x,int y,String[][] goBang,String fh){
		int length = 20;
		int count = 1;
		for (int i = y+1; i < length; i++) {
			if (goBang[i][x].equals(fh)) {
				count++;
			}else {
				break;
			}
		}
		for (int i = y-1; i >= 0; i--) {
			if (goBang[i][x].equals(fh)) {
				count++;
			}else {
				break;
			}
		}
		//System.out.println(count);
		if (count >= 5) {
			return true;
		}
		return false;
	}
	//左上到右下方向
	public static boolean xyAxis(int x,int y,String[][] goBang,String fh){
		int length = 20;
		int count = 1;
		int index = 1;
		for (int i = x+1; i < length; i++) {
			if (goBang[y+index][i].equals(fh)) {
				count++;
			}else {
				break;
			}
			index++;
		}
		index=1;
		for (int i = x-1; i >= 0; i--) {
			if (y-index<0) {
				break;
			}
			if (goBang[y-index][i].equals(fh)) {
				count++;
			}else {
				break;
			}
			index++;
		}
		//System.out.println(count);
		if (count >= 5) {
			return true;
		}
		return false;
	}
	//右上到左下
	public static boolean yxAxis(int x,int y,String[][] goBang,String fh){
		int length = 20;
		int count = 1;
		int index = 1;
		for (int i = x+1; i < length; i++) {
			if (y-index<0) {
				break;
			}
			if (goBang[y-index][i].equals(fh)) {
				count++;
			}else {
				break;
			}
			index++;
		}
		index=1;
		for (int i = x-1; i >= 0; i--) {
			if (goBang[y+index][i].equals(fh)) {
				count++;
			}else {
				break;
			}
			index++;
		}
		System.out.println(count);
		if (count >= 5) {
			return true;
		}
		return false;
	}

}

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