java中DOM解析XML文件奇葩的错误 java.lang.NullPointerException
代码如下：
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public class LoadXml extends Activity {
private final static String TAG="LoadXml";
public static Context context = null;
Document document = null;
NodeList childsNodes = null;
DocumentBuilderFactory factory = null;
DocumentBuilder builder = null;
InputStream inputStreams = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button button1=(Button)findViewById(R.id.button1);
button1.setOnClickListener(button1OnClickListener);
}
OnClickListener button1OnClickListener=new OnClickListener(){
@Override
public void onClick(View v) {
Log.d(TAG, "onClick");
getComplateXml();
}
};
public void getComplateXml(){
Log.d(TAG, "123");
try {
Log.d(TAG, "getComplateXml");
readUserConfig();
// int j = 0;
// for (int i = 0; i childsNodes.getLength(); i++) {
// Log.d(TAG, "1");
// Node node = (Node) childsNodes.item(i);
// Log.d(TAG, "2");
// ContentResolver contentResolver = this.context
// .getContentResolver();
// Log.d(TAG, "3");
// Uri insertUri = Uri.parse("content://com.huawei.biz.LoadContentProvider/STUDENT");
// Log.d(TAG, "4");
// ContentValues values = new ContentValues();
// values.put("name", node.getNodeName());
// Log.d(TAG, node.getNodeName());
//
// values.put("id", node.getFirstChild().getNodeValue());
// Log.d(TAG, node.getFirstChild().getNodeValue());
//
// values.put("Photo",DataManager.getDrawableList().get(j));
// Log.d(TAG, DataManager.getDrawableList().get(j).toString());
// contentResolver.insert(insertUri, values);
// j++;
// }
} catch (Exception e) {
e.printStackTrace();
}
}
private void readUserConfig() throws Exception{
Log.d(TAG, "readUserConfig");
Log.d(TAG, "1");
factory = DocumentBuilderFactory.newInstance();
Log.d(TAG, "2");
builder = factory.newDocumentBuilder();
Log.d(TAG, "3");
inputStreams = LoadXml.context.getResources().getAssets().open("student.xml");
Log.d(TAG, "4");
document = builder.parse(inputStreams);
Log.d(TAG, "5");
childsNodes = document.getDocumentElement().getChildNodes();
Log.d(TAG, "6");
}
}
java面试题：一个人早上八点上山，晚上八点到达山顶。第二天早上八点下山，晚上八点到达山底。
java面试题的解析方式（思路如下）：
public static void main(String[] args) {
// TODO Auto-generated method stub
int up = 8;
int down = 8;
while(up=20){
if((up == 20-6) (up == 20-6)){
System.out.println("在"+up+"时到达同一地点");
break;
}
up += 1;
down += 1;
}
}
微软面试题的背后
微软的奇葩面试题答案并不重要，重要的是思考过程，而思考过程体现了你是否拥有公司所看重的能力，不仅是微软，其他公司的面试也是为了测试你的某种能力，如果你提前培养了这种能力，相当于知道了面试的“考纲”，在面试中自然就从容不迫，游刃有余了。
平时要知道转化能力是看透问题，然后找到解决方案的能力。所以转化能力最重要的是如何看透问题，也就是你思考问题的方式。
教我写下小代码吧 java
interface Instrument{
void play();
}
class Piano implements Instrument{
public void play() {
System.out.println("play Piano");
}
}
class Violin implements Instrument{
public void play() {
System.out.println("play Violin");
}
}
public class InstrumentTest{
public static void main(String[] args) {
Instrument i1 = new Piano();
Instrument i2 = new Violin();
i1.play();
i2.play();
}
}
java线程的经典代码
package threadgroup;
class ThreadDemo3 extends Thread {
private String name;
private int delay;
public ThreadDemo3(String sname, int i_delay) {
name = sname;
delay = i_delay;
}
public void run() {
try {
sleep(delay);
} catch (InterruptedException e) {
}
System.out.println("多线程测试！\n" + name + "\n" + delay);
}
}
public class testMyThread {
public static void main(String[] args) {
ThreadDemo3 th1,th2,th3;
th1 = new ThreadDemo3("线程1", (int) (Math.random() * 900));
th2 = new ThreadDemo3("线程2", (int) (Math.random() * 900));
th3 = new ThreadDemo3("线程3", (int) (Math.random() * 900));
th1.start();
th2.start();
th3.start();
}
}
package threadgroup;
public class threadDemo {
public static void main(String[] args) {
Thread t = Thread.currentThread();
t.setName("你好吗？");
System.out.println("正在进行的Thread是：" + t);
try {
for (int i = 0; i 5; i++) {
System.out.println("我不叫穆继超" + i);
Thread.sleep(3000);
}
} catch (Exception e) {
// TODO: handle exception
System.out.println("Thread has wrong" + e.getMessage());
}
}
}
package threadgroup;
public class threadDemo2 implements Runnable {
public threadDemo2() {
Thread t1 = Thread.currentThread();
t1.setName("第一个主进程");
System.out.println("正在运行" + t1);
Thread t2 = new Thread(this, "");
System.out.println("在创建一个进程");
t2.start();
try {
System.out.println("使他进入第一个睡眠状态");
Thread.sleep(2000);
} catch (InterruptedException e) {
System.out.println("Thread has wrong" + e.getMessage());
}
System.out.println("退出第一个进程");
}
public void run() {
try {
for (int i = 0; i 5; i++) {
System.out.println("进程" + i);
Thread.sleep(3000);
}
} catch (InterruptedException e) {
// TODO: handle exception
System.out.println("Thread has wrong" + e.getMessage());
}
System.out.println("退出第二个进程");
}
public static void main(String[] args) {
new threadDemo2();
}
}
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