以下是我在上一家公司出的java笔试题，有些难度，感兴趣的同学可以做做看。
---Question---
1.What is the output of the following program
public class Foo {
public static void main(String[] args){
Map
byte[] key = "abcd".getBytes();
m.put(key, "abcd");
System.out.println(m.containsKey(key));
System.out.println(m.containsKey("abcd"));
System.out.println(m.containsKey("abcd".getBytes()));
}
}
a) true,true,false b)true,false,false c)true,true,true d) false,false,false e)Program throws an exception
2. What is the proper string filled in the following program
Public class Foo {
public static void main(String[] args) {
String s=”1\\2\\3\\4”;
//split the string with “\”
String []result = s.split(“____”);
for(String r:result){
System.out.println(r);
}
}
}
a) \ b) \\ c) \\\ d)\\\\ e)\\\\\
3. What is the output of the following program
public class Foo {
public static void main(String[] args) {
char[] c = new char[] { '1' };
String s = new String(c);
System.out.println("abcd" + c);
System.out.println("abcd" + s);
}
}
a) Compile error b)abcd1,abcd1 c) abcd49,abcd1 d) Program throws an exception e)none of above
4. Which class is threading safe which one object can be used between multi-threads without extra synchronized
a) Vector b) HashMap c) ArrayList d)StringBuilder e)HashSet
5. What is the output of the following program
public class Foo {
public static void main(String[] args) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] b = new byte[]{(byte)0x0,(byte)0x1,(byte)0x2};
baos.write(b);
baos.write(0x0102);
byte[] result = baos.toByteArray();
ByteArrayInputStream bais = new ByteArrayInputStream(result);
System.out.println(bais.available());
}
}
a) 0 b) 1 c)4 d) 5 e) Program throws an exception
6. What is return value of function “calc”
public class Foo {
public static int calc() throws IOException{
int ret = 0;
try{
++ret;
throw new IOException("try");
}
catch(IOException ioe){
--ret;
return ret;
}
finally{
++ret;
return ret;
}
}
}
a) 0 b) 1 c)2 d)3 e) throws an exception
7. What is the output of the following program
public class Foo {
public static class Value {
private int value;
public int get(){
return value;
}
public void set(int v){
value = v;
}
}
public static class Values implements Iterable
public Values(int capacity){
this.capacity = capacity;
}
int count =1 ;
int capacity;
Value v = new Value();
public Iterator
return new Iterat