java 显示不是内部或外部命令，也不是可运行程序

原因：这是因为安装java时把jdk的路径和jre的路径选择成一样，就造成覆盖了，这时候你在lib下也找不都toolsjar和dtjar

解决：

如果只需要使用javac命令其实不需要这么复杂的，可以直接把新建的JAVA_HOME、CLASSPATH这两个变量和PATH变量中的JAVA_HOME%\bin;%JAVA_HOME%\jre\bin删了，然后在Path变量的头部添加如下路径：

C:\Program Files\Java\jdk150\bin;就可以了。

扩展资料：

关于上述中配置的path

配置系统变量path，在里边加入路径值

;%JAVA_HOME%/bin;%JAVA_HOME%/jre/bin;（加在中间的配置方式为，即C:\Program Files (x86)\Common Files\Oracle\Java\javapath）

%JAVA_HOME%/bin;%JAVA_HOME%/jre/bin;（加在首部）

;%JAVA_HOME%/bin;%JAVA_HOME%/jre/bin（加在尾部）

贪吃蛇程序:

GreedSnakejava (也是程序入口):

import javaawtBorderLayout;

import javaawtCanvas;

import javaawtColor;

import javaawtContainer;

import javaawtGraphics;

import javaawteventKeyEvent;

import javaawteventKeyListener;

import javautilIterator;

import javautilLinkedList;

import javaxswingJFrame;

import javaxswingJLabel;

import javaxswingJPanel;

public class GreedSnake implements KeyListener {

JFrame mainFrame;

Canvas paintCanvas;

JLabel labelScore;// 计分牌

SnakeModel snakeModel = null;// 蛇

public static final int canvasWidth = 200;

public static final int canvasHeight = 300;

public static final int nodeWidth = 10;

public static final int nodeHeight = 10;

// ----------------------------------------------------------------------

// GreedSnake():初始化游戏界面

// ----------------------------------------------------------------------

public GreedSnake() {

// 设置界面元素

mainFrame = new JFrame("GreedSnake");

Container cp = mainFramegetContentPane();

labelScore = new JLabel("Score:");

cpadd(labelScore, BorderLayoutNORTH);

paintCanvas = new Canvas();

paintCanvassetSize(canvasWidth + 1, canvasHeight + 1);

paintCanvasaddKeyListener(this);

cpadd(paintCanvas, BorderLayoutCENTER);

JPanel panelButtom = new JPanel();

panelButtomsetLayout(new BorderLayout());

JLabel labelHelp;// 帮助信息

labelHelp = new JLabel("PageUp, PageDown for speed;", JLabelCENTER);

panelButtomadd(labelHelp, BorderLayoutNORTH);

labelHelp = new JLabel("ENTER or R or S for start;", JLabelCENTER);

panelButtomadd(labelHelp, BorderLayoutCENTER);

labelHelp = new JLabel("SPACE or P for pause", JLabelCENTER);

panelButtomadd(labelHelp, BorderLayoutSOUTH);

cpadd(panelButtom, BorderLayoutSOUTH);

mainFrameaddKeyListener(this);

mainFramepack();

mainFramesetResizable(false);

mainFramesetDefaultCloseOperation(JFrameEXIT_ON_CLOSE);

mainFramesetVisible(true);

begin();

}

// ----------------------------------------------------------------------

// keyPressed():按键检测

// ----------------------------------------------------------------------

public void keyPressed(KeyEvent e) {

int keyCode = egetKeyCode();

if (snakeModelrunning)

switch (keyCode) {

case KeyEventVK_UP:

snakeModelchangeDirection(SnakeModelUP);

break;

case KeyEventVK_DOWN:

snakeModelchangeDirection(SnakeModelDOWN);

break;

case KeyEventVK_LEFT:

snakeModelchangeDirection(SnakeModelLEFT);

break;

case KeyEventVK_RIGHT:

snakeModelchangeDirection(SnakeModelRIGHT);

break;

case KeyEventVK_ADD:

case KeyEventVK_PAGE_UP:

snakeModelspeedUp();// 加速

break;

case KeyEventVK_SUBTRACT:

case KeyEventVK_PAGE_DOWN:

snakeModelspeedDown();// 减速

break;

case KeyEventVK_SPACE:

case KeyEventVK_P:

snakeModelchangePauseState();// 暂停或继续

break;

default:

}

// 重新开始

if (keyCode == KeyEventVK_R || keyCode == KeyEventVK_S

|| keyCode == KeyEventVK_ENTER) {

snakeModelrunning = false;

begin();

}

}

// ----------------------------------------------------------------------

// keyReleased（）：空函数

// ----------------------------------------------------------------------

public void keyReleased(KeyEvent e) {

}

// ----------------------------------------------------------------------

// keyTyped（）：空函数

// ----------------------------------------------------------------------

public void keyTyped(KeyEvent e) {

}

// ----------------------------------------------------------------------

// repaint（）：绘制游戏界面（包括蛇和食物）

// ----------------------------------------------------------------------

void repaint() {

Graphics g = paintCanvasgetGraphics();

// draw background

gsetColor(ColorWHITE);

gfillRect(0, 0, canvasWidth, canvasHeight);

// draw the snake

gsetColor(ColorBLACK);

LinkedList na = snakeModelnodeArray;

Iterator it = naiterator();

while (ithasNext()) {

Node n = (Node) itnext();

drawNode(g, n);

}

// draw the food

gsetColor(ColorRED);

Node n = snakeModelfood;

drawNode(g, n);

updateScore();

}

// ----------------------------------------------------------------------

// drawNode（）：绘画某一结点（蛇身或食物）

// ----------------------------------------------------------------------

private void drawNode(Graphics g, Node n) {

gfillRect(nx nodeWidth, ny nodeHeight, nodeWidth - 1,

nodeHeight - 1);

}

// ----------------------------------------------------------------------

// updateScore（）：改变计分牌

// ----------------------------------------------------------------------

public void updateScore() {

String s = "Score: " + snakeModelscore;

labelScoresetText(s);

}

// ----------------------------------------------------------------------

// begin（）：游戏开始，放置贪吃蛇

// ----------------------------------------------------------------------

void begin() {

if (snakeModel == null || !snakeModelrunning) {

snakeModel = new SnakeModel(this, canvasWidth / nodeWidth,

thiscanvasHeight / nodeHeight);

(new Thread(snakeModel))start();

}

}

// ----------------------------------------------------------------------

// main（）：主函数

// ----------------------------------------------------------------------

public static void main(String[] args) {

GreedSnake gs = new GreedSnake();

}

}

Nodejava:

public class Node {

int x;

int y;

Node(int x, int y) {

thisx = x;

thisy = y;

}

}

SnakeModeljava:

import javautilArrays;

import javautilLinkedList;

import javautilRandom;

import javaxswingJOptionPane;

public class SnakeModel implements Runnable {

GreedSnake gs;

boolean[][] matrix;// 界面数据保存在数组里

LinkedList nodeArray = new LinkedList();

Node food;

int maxX;// 最大宽度

int maxY;// 最大长度

int direction = 2;// 方向

boolean running = false;

int timeInterval = 200;// 间隔时间（速度）

double speedChangeRate = 075;// 速度改变程度

boolean paused = false;// 游戏状态

int score = 0;

int countMove = 0;

// UP和DOWN是偶数，RIGHT和LEFT是奇数

public static final int UP = 2;

public static final int DOWN = 4;

public static final int LEFT = 1;

public static final int RIGHT = 3;

// ----------------------------------------------------------------------

// GreedModel():初始化界面

// ----------------------------------------------------------------------

public SnakeModel(GreedSnake gs, int maxX, int maxY) {

thisgs = gs;

thismaxX = maxX;

thismaxY = maxY;

matrix = new boolean[maxX][];

for (int i = 0; i < maxX; ++i) {

matrix[i] = new boolean[maxY];

Arraysfill(matrix[i], false);// 没有蛇和食物的地区置false

}

// 初始化贪吃蛇

int initArrayLength = maxX > 20 10 : maxX / 2;

for (int i = 0; i < initArrayLength; ++i) {

int x = maxX / 2 + i;

int y = maxY / 2;

nodeArrayaddLast(new Node(x, y));

matrix[x][y] = true;// 蛇身处置true

}

food = createFood();

matrix[foodx][foody] = true;// 食物处置true

}

// ----------------------------------------------------------------------

// changeDirection():改变运动方向

// ----------------------------------------------------------------------

public void changeDirection(int newDirection) {

if (direction % 2 != newDirection % 2)// 避免冲突

{

direction = newDirection;

}

}

// ----------------------------------------------------------------------

// moveOn():贪吃蛇运动函数

// ----------------------------------------------------------------------

public boolean moveOn() {

Node n = (Node) nodeArraygetFirst();

int x = nx;

int y = ny;

switch (direction) {

case UP:

y--;

break;

case DOWN:

y++;

break;

case LEFT:

x--;

break;

case RIGHT:

x++;

break;

}

if ((0 <= x && x < maxX) && (0 <= y && y < maxY)) {

if (matrix[x][y])// 吃到食物或者撞到身体

{

if (x == foodx && y == foody)// 吃到食物

{

nodeArrayaddFirst(food);// 在头部加上一结点

// 计分规则与移动长度和速度有关

int scoreGet = (10000 - 200 countMove) / timeInterval;

score += scoreGet > 0 scoreGet : 10;

countMove = 0;

food = createFood();

matrix[foodx][foody] = true;

return true;

} else

return false;// 撞到身体

} else// 什么都没有碰到

{

nodeArrayaddFirst(new Node(x, y));// 加上头部

matrix[x][y] = true;

n = (Node) nodeArrayremoveLast();// 去掉尾部

matrix[nx][ny] = false;

countMove++;

return true;

}

}

return false;// 越界（撞到墙壁）

}

// ----------------------------------------------------------------------

// run():贪吃蛇运动线程

// ----------------------------------------------------------------------

public void run() {

running = true;

while (running) {

try {

Threadsleep(timeInterval);

} catch (Exception e) {

break;

}

if (!paused) {

if (moveOn())// 未结束

{

gsrepaint();

} else// 游戏结束

{

JOptionPaneshowMessageDialog(null, "GAME OVER",

"Game Over", JOptionPaneINFORMATION_MESSAGE);

break;

}

}

}

running = false;

}

// ----------------------------------------------------------------------

// createFood():生成食物及放置地点

// ----------------------------------------------------------------------

private Node createFood() {

int x = 0;

int y = 0;

do {

Random r = new Random();

x = rnextInt(maxX);

y = rnextInt(maxY);

} while (matrix[x][y]);

return new Node(x, y);

}

// ----------------------------------------------------------------------

// speedUp():加快蛇运动速度

// ----------------------------------------------------------------------

public void speedUp() {

timeInterval = speedChangeRate;

}

// ----------------------------------------------------------------------

// speedDown():放慢蛇运动速度

// ----------------------------------------------------------------------

public void speedDown() {

timeInterval /= speedChangeRate;

}

// ----------------------------------------------------------------------

// changePauseState(): 改变游戏状态（暂停或继续）

// ----------------------------------------------------------------------

public void changePauseState() {

paused = !paused;

}

}

/

  输出

  @param year  年份

 /

private void output(int year){

    boolean bo = false;  //是否是闰年

    if (year % 4 == 0 && year % 400 == 0){

        bo = true;

    }

    for (int i = 1; i <= 12; i++){

        for (int n = 0; n < 3; n++){

            Systemoutprintln("2017年" + i + "月" + n + "3日");

            Systemoutprintln("2017年" + i + "月" + n + "6日");

            if (bo && i == 2){

                Systemoutprintln("2017年" + i + "月" + n + "9日");

            }

        }

    }

}

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