有用的面试题
n addMe(myChi.x, myChi.y, myChi.z);
}
public int addMe(int x, int y) {
return this.x + x + this.y + y;
}
}
public class MySomeOne {
public static void main(String args[]) {
MyChild myChi = new MyChild(10, 20, 30);
MyParent myPar = new MyParent(10, 20);
int x = myChi.addMe(10, 20, 30);// 120
int y = myChi.addMe(myChi);// 120
int z = myPar.addMe(myPar);// 60
System.out.println(x + y + z);
}
}
4、What will happen when you attempt to compile and run the following code? （E）
interface MyInterface {
}
public class MyInstanceTest implements MyInterface {
static String s;
public static void main(String args[]) {
MyInstanceTest t = new MyInstanceTest();
if (t instanceof MyInterface) {
System.out.println("I am true interface");
} else {
System.out.println("I am false interface");
}
if (s instanceof String) {
System.out.println("I am true String");
} else {
System.out.println("I am false String");
}
}
}
A、compile time error
B、runtime error
C、prints: “I am true interface” followed by “I am true String”
D、prints: “I am false interface” followed by “I am false String”
E、prints: “I am true interface” followed by “I am false String”
F、prints: “I am false interface” followed by “I am true String”
只有当一个对象实例化之后才有可能知道其具体的类型。
5、What results from attempting to compile and run the following code? （D）
public class Ternary {
public static void main(String args[]) {
int a = 5;
System.out.println("Value is - " + ((a < 5) ? 9.0 : 9)); ? 数据类型的自动转换 9.0
}
}
A、print:Value is -9B、print:Value is -5C、Compilation errorD、None of these
6、What will be the result of executing the following code? （D）
public static void main(String args[]) {
char digit = 'a';
for (int i = 0; i < 10; i++) {
switch (digit) {
case 'x': {
int j = 0;
System.out.println(j);
}
default: {
int j = 100;
System.out.println(j);
}
}
}
int i = j;
System.out.println(i);
}
A、100 will be printed 11 times.
B、100 will be printed 10 times and then there will be a runtime exception
C、The code will not compile because the variable i cannot be declared twice within the mani() method.
D、The code will not compile because the variable j cannot be declared twice within the switch statement.
E、None of these.
7、Which of the following collection classes from java.util package are Thread safe? （D）
A、VectorB、ArrayListC、HashMapD、Hashtable
8、What will happen when you attempt to compile and run the following code? （A）
class MyThread extends Thread {
public void run() {
System.out.println("MyThread: run()");
}
publi
c void start() {
System.out.println("MyThread: start()");
}
}
class MyRunnable implements Runnable {
public void run() {
System.