我对变量或方法应该是静态的时候有点困惑。我开发了一个包含多个类，变量和方法的应用程序，很少使用关键字static。但它的工作令人满意。你能告诉我，我是否犯了错误，为什么。以下是我的代码示例：
public class GameActivity extends AppCompatActivity {
public String[] mots = {"AFTERNOON", "AIRPORT","AVENUE","BETWEEN", "BUS", "CAB", "COAST","DAY",
"DIFFERENCE","DOLLARS","ENGLISH","FRENCH","GOOD","GOODBYE","HOUR","IMPROVE","LATER",
"LOCAL","MARGARET","NAME","NINE","NUMBER","ONLY","PHONE","PLANE","SAME","SHARE",
"SIDEWALK","STATES","SUNDAY","THERE","TIME","TWELVE","UNITED","UNIVERSITY","VERY",
"WEST","WHEN","WOMAN","YOUNG"};
public String[] alphabet = {"A","B","C","D","E","F","G","H","I","J","K","L","M",
"N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
public String mysteryWord = "vide";
//public int nombreDeLettres;
public int numeroImage = 1;
public boolean jeuFini = false;
public int lettresDevinees = 0;
public int wins = 0;
public int losses = 0;
public int numberOfMots;
int numeroAuHasard;
public Boolean maLettreAServi = false;
public ArrayList<CharSequence> lettresEssayees = new ArrayList<>();
public Button monBouton;
public TextView monTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_game);
AdView mAdView = (AdView) findViewById(R.id.adView);
AdRequest request = new AdRequest.Builder()
.addTestDevice("AC98C820A50B4AD8A2106EDE96FB87D4") // adds my test phone
.build();
mAdView.loadAd(request);
// une des solutions pour rendre la zone trado scrollable
TextView myXmlContent = (TextView)findViewById(R.id.zone_trado_scrollable);
myXmlContent.setMovementMethod(new ScrollingMovementMethod());
// écouteurs de tous les boutons actifs
ecouteursDeBoutons();
}
// joue une lettre
public void playLetter(final String letter) {
Resources res = getResources();
final int resId = res.getIdentifier(letter, "id", getPackageName());
monTextView = (TextView) this.findViewById(R.id.zone_trado_scrollable);
final TextView maLettre = (TextView) this.findViewById(resId);
maLettre.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
if (!jeuFini) { // il faut mettre ce test _dans_ le onClick(View v)
if (!mysteryWord.equalsIgnoreCase("vide")) {
if (!lettresEssayees.contains(maLettre.getText())) {
// on teste que la lettre n'a pas déjà été essayée
maLettreAServi = false;
// boucle de test de lettre
for (int i = 0; i < mysteryWord.length(); i++) {
if (String.valueOf(mysteryWord.charAt(i)).equals(maLettre.getText())) {
int j = i + 1; // car dans le layout xml les id des positions commencent à 1
//monTextView.append("\nyou correctly found " + maLettre.getText() + " at position " + j);
final int resId = getResources().getIdentifier("position" + j, "id", getPackageName());
final TextView lettreADeviner = (TextView) GameActivity.this.findViewById(resId);
lettreADeviner.setText(maLettre.getText());
maLettreAServi = true;
lettresDevinees++;
}
}
maLettre.setText(""); // on efface de l'alphabet la lettre essayée
lettresEssayees.add(maLettre.getText());
// on la met dans l'arraylist lettresEssayees
// afin de ne pas la réessayer
// noter que java comprend qu'il s'agit d'un caractère et non d'une string
// test pour effacer de l'alphabet une lettre qui a servi
if (!maLettreAServi) {
// incrémenter le pendu
numeroImage++;
if (numeroImage < 10) {
ImageView monImage = (ImageView) findViewById(R.id.imagePendu);
final int imageId = getResources().getIdentifier("pendu" + numeroImage, "drawable", getPackageName());
monImage.setImageResource(imageId);
} else {
ImageView monImage = (ImageView) findViewById(R.id.imagePendu);
final int imageId = getResources().getIdentifier("pendu10", "drawable", getPackageName());
monImage.setImageResource(imageId);
jeuFini = true;
monTextView.setText(Html.fromHtml("<font color=\"red\">you lost</font>"));
monTextView.append("\nthe word was "+mysteryWord);
losses++;
TextView nombrePertes = (TextView) findViewById(R.id.nr_losses);
nombrePertes.setText("" + losses); // pas réussi à utiliser toString(), alors j'utilise cette converstion
}
}
// test qu'on a trouvé le mot mystère
if (lettresDevinees == mysteryWord.length()) {
jeuFini = true;
// randomisation des félicitations
Random generator = new Random();
int randomIndex = generator.nextInt(3);
if(randomIndex == 0){
monTextView.setText(Html.fromHtml("<font color=\"blue\">bravo!</font>"));}
else if(randomIndex == 1){
monTextView.setText(Html.fromHtml("<font color=\"blue\">fantastic!</font>"));}
else if (randomIndex == 2) {
monTextView.setText(Html.fromHtml("<font color=\"blue\">you won</font>"));}
// rappel de ce qu'était le mot à deviner
monTextView.append("\nthe word was indeed " + mysteryWord);
String son = mysteryWord.toLowerCase()+"1";
final int resRaw = getResources().getIdentifier(son, "raw", getPackageName());
final MediaPlayer mp = MediaPlayer.create(GameActivity.this, resRaw);
mp.start();
wins++;
TextView nombreGains = (TextView) findViewById(R.id.nr_wins);
nombreGains.setText("" + wins); // pas réussi à utiliser toString(), alors j'utilise cette converstion
}
}
} else {
monTextView.setText("click on Select word first");
}
}
}
});
}
...
}
答案 0 :(得分：8)
java中的static关键字主要用于内存管理。我们可以将java static keyword与变量，方法，块和嵌套类一起应用。 如果我们谈论静态变量，那么我们将其区分为 静态变量可用于引用所有对象的公共属性（对于每个对象而言不是唯一的），例如公司员工姓名，学生姓名等。
静态变量在类加载时只在类区域中获取一次内存。
如果我们谈论它使用： 当你想要共享你的变量或方法时，只需要在整个类中单个副本而不创建不同的副本，你应该使用static。
<强>优点 它使程序存储器有效（即节省内存）。
答案 1 :(得分：1)
可以使用类名直接访问静态变量，它将具有单个实例。
YourActivity.staticVariableName=something;
从应用程序的任何位置访问变量很有帮助。但请注意，在整个应用程序结束之前，它有一生。因此它在整个应用程序生命周期内消耗该内存。因此，请牢记这一点。
答案 2 :(得分：1)
通常，所有与类对象无关且适用于整个对象的常量和变量都应声明为static。因此，查看示例代码时，您应该将mots，alphabet声明为static和final，因为没有必要为您的每个对象都单独复制这些代码。
如果你想在其他地方使用GameActivity关键字，那么关键字static也允许你通过使用GameActivity.mots类名final来访问其他类中的这些常量，public final static String[] mots = {"AFTERNOON", "AIRPORT","AVENUE","BETWEEN", "BUS", "CAB", "COAST","DAY",
"DIFFERENCE","DOLLARS","ENGLISH","FRENCH","GOOD","GOODBYE","HOUR","IMPROVE","LATER",
"LOCAL","MARGARET","NAME","NINE","NUMBER","ONLY","PHONE","PLANE","SAME","SHARE",
"SIDEWALK","STATES","SUNDAY","THERE","TIME","TWELVE","UNITED","UNIVERSITY","VERY",
"WEST","WHEN","WOMAN","YOUNG"};
public final String[] alphabet = {"A","B","C","D","E","F","G","H","I","J","K","L","M",
"N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
关键字可以保证没有人可以改变这些。
<div class="form-group">
<label for="Course" class="col-sm-4 control-label">Dashbord *</label>
<div class="col-sm-4" id="multicourse">
<select id="Course" name="options[]" multiple="multiple" style="width:100%">
<option value="1" >Sales</option>
<option value="2" >Students</option>
<option value="3" >Quetion</option>
<option value="4" >Test</option>
<option value="5" >Test Series</option>
<option value="6" >Student</option>
<option value="7" >Validity</option>
<option value="8" >Disk Space</option>
<option value="9" >Student Graph</option>
<option value="10" >Date</option>
</select>
</div>
</div>
答案 3 :(得分：1)
我只想在 pgiitu 和 Piyush Gupta 的答案中添加另一个观点。
根据Java docs： 如果您的变量存储一个常量值，例如static final int NUM_GEARS = 6，则约定会略有变化，将每个字母大写并用后缀字符分隔后续单词。按照惯例，下划线字符从未在别处使用过。
因此，正如 pgiitu 所提到的mots和alphabet应该声明为static和final。但是，通过命名约定，您应该将它们分别重命名为MOTS和ALPHABET。
答案 4 :(得分：0)
当你想要共享你的变量或方法时，只需要通过类复制而不创建不同的副本，你应该使用static ..而且接口变量默认是static和final。如果你想了解更多
，首先应该选择基本的JAVA概念答案 5 :(得分：0)
静态变量。类似静态方法的概念。 了解更多信息请点击此链接 http://www.javatpoint.com/static-keyword-in-java