下列程序代码执行完毕后,多少个字节被写入到文件t.dat中?(C)import java.io.*;public class Test { public static void main(String[] args) throws IOException { DataOutputStream output = new DataOutputStream( new FileOutputStream("t.dat")); output.writeChars("ABCD"); output.close(); }}
A. 2 bytes
B. 4 byte
C. 8 bytes
D. 12 bytes
E. 16 bytes
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可以使用下面哪个方法强制一个线程等待其它线程执行完毕 (D)A:sleep(long milliseconds)B:yield()C:stop()D:join()public class Base{int x;static int z;public Base() { z++;(1)}Public static void main(String[] args){ int y; Base b=new Base(); System.out.print(Base.z);(2) System.out.print(x);(3) System.out.print(y);(4)}}会出错的语句是()
A. (1)
B. (2)
C. (3)
D. (4)
13.假设A类有如下定义,设a是A类的一个实例,下列语句调用哪个是错误的?()class A { int i; static String s;void method1() { }static void method2() { }}
A. System.out.println(a.i);
B. a.method1();
C. A.method1();
D. A.method2();
运行以下程序会抛出哪种异常?()publicclassTest{public static void main(String[] args) Object o = null;System.out.println(o);}
ArithmeticException
B. ArrayIndexOutOfBoundsException
C. StringIndexOutOfBoundsException
D. no Exception
E. NullPointerException
执行如下程序后b的值为? ()int x, b=0; for(x = 0; x <= 5; ++x){ if (x == 2) continue; ++b; }
A. 5
B. 4
C. 3