JAVA认证历年真题-SCJP考试真题和解析[1].doc

JAVA认证历年真题:SCJP考试真题和解析[1]例题1: Choose the three valid identifiers from those listed beloeClassB.$byteC・ constD._okE.3_case解答：A, B, D点评：Java中的标示符必须是字母、美元符($)或下划线(_)开头。

关键字与保留字不能作为标示符。

选项C中的const是Java的保留字，所以不能作标示符。

选项E中的3_case以数字开头，违反了Java的规则。

例题2：Ho.gc()・C.Call System.gc(), passing in a reference to the object to be garbage collected・D.Call Runtime.gc().E.Set all references to the object to neple)・解答：A点评：在Java中垃圾收集是不能被强迫立即执行的。

调用System.gc()或Runtime.gc()静态方法不能保证垃圾收集器的立即执行，因为，也许存在着更高优先级的线程。

所以选项B、D不正确。

选项C的错误在于，System.gc()方法是不接受参数的。

选项E 中的方法可以使对象在下次垃圾收集器运行时被收集。

例题3：Consider the follo.out.println( "I am an int.v );4.}5.void test(String s) {6.System.out.println( “I am a string.v );7.}&9.public static void main(String argsf]) {10.Test t=neents beloethods cannot be overridden.B.Line 12 ent.C.The code an int.E. The code a String.解答：D点评：在第12行，16位长的char型变量ch在编译时会自动转化为一个32位长的int型,并在运行时传给void test(int i)方法。

例题4：y Text Area, javaB.B etade to super(nroent about the garbage collection mechanism are true?A.Garbage collection require additional programe code in cases ultiple threads are running・B.The programmer can indicate that a reference through a local variable is no longer of interest.C.The programmer has a mechanism that explicity and immediately frees the memory used by Java objects・D.The garbage collection mechanism can free the memory used by Java Object at explection time・E.The garbage collection system never reclaims memory from objects ethod:1)public void method(){2)String a,b;3)a二nee over” );5)System.out・println(a+b+” ok” );6)a=null;7)a=b;8)System.out.println(a);9)}In the absence of piler optimization, ethod called getID ethod?A.It is a reference to the object directly affected by the cause of the event.B.11 is an indication of the nature of the cause of the event.C.It is an indication of the position of the mouse ouse click, it is an indication of the text under the mouse at the time of the event.E.It tells the state of certain keys on the keybord at the time of the event.F.It is an indication of the time at ent about listener is true?A.Most ponent alloultiple listeners to be added.B.If multiple listener be add to a single ponent, the event only affected one listener.C・ ponent don?t alloultiple listeners to be add・D.The listener mechanism alloethod as many times as is needed, specifying as many different listeners as your design require.4o A、D控件可以同时使用多个"addXxxxListener方法加入多个监听器。

并且当多个监听器加入到同一控件中时，事件可以响应多个监听器，响应是没有固定顺序的。

5.Give the follople{public static void main(String args[] ){int 1=0;do{System.out.println( u Doing it for 1 is:" +1);}.out.println( “Finish” );}}yClass{//do other thing***} E. class MyClass{//do something-••}15o A、EX处可以是一个输入，包的定义，类的定义。

由于常量或变量的声明只能在类中或方法中，故不能选择C；由于在一个文件中只能有一个public类，故不能选择D。

16.Give this class outline:class Example {private int x;//rest of class body-}Assuming that x invoked by the code java Example, ent can made x be directly accessible in main() method of Example.java?A.Change private int x to public int xB.change private int x to static int xC.Change private int x to protected int xD.change private int x to final int x16o B静态方法除了自己的参数外只能直接访问静态成员。

访问非静态成员，必须先实例化本类的一个实例，再用实例名点取。

17.the piece of preliminary analsis any unrelated parts of a project“The polygon object is a draation stored in a vector, a color, length and ember variable should be accessible only by same package, odifer odiferD.private18o C此题考点是高级访问控制。

请考生查阅高级访问控制说明表格。

19.ethod in a java class corrected?A.public native void method() {}B.public native void method();C.public native method();D.public void method(){native;}E.public void native method();19o Bnative关键字指明是对木地方法的调用，在JAVA中是只能访问但不能写的方法，它的位置在访问权限修饰语的后面及返回值的前面。

20.odifer should be applied to a declaration of a class member variable for the value of variable to remain constant after the creation of the object? 20 o final定义常量的方法是在变量定义前加final关键字。

21.ain() method return of a application?A.StringB.byteC.charD.void21o Dmain()方法没有返回值，所以必须用void修饰。

main()方法的返回值不能任意修改。

22.ent of main() method of application?A.String argsB.String ar[]C.Char args[][]D.StringBuffer arg[]22 o Bmain()方法的参数是字符串数组，参数名可以任意定义。

23.“The Employee object is a person, An Employee has appointment store in a vector, a hire date and a number of dependent ”short ansent declare a class of Employee・23o public class Employee extends Person这也是真实考试中常见的一种题型。

要注意题目叙述中“is a” 表示“extends”的含义。

24.Give the follople{public Example(){//do something}protected Example(int i){//do something}protected void method(){//do something}}public class Hello extends Example {//member method and member variable}ethods are coiTected added to the class Hello?A.public void Example(){}B.public void method(){}C.protected void method(){}D.private void method(){}24o A、B、C考察的知识点是方法覆盖，其中要注意的是方法覆盖时，子类方法的访问权限不能小于父类方法的访问权限。