面向面试准备、在线测试、教程与实战练习的学习平台

通过聚焦学习路径、模拟测试和面试实战内容持续提升技能。

WithoutBook 将分主题面试题、在线练习测试、教程和对比指南整合到一个响应式学习空间中。

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面试准备

Core Java 面试题与答案

Test your skills through the online practice test: Core Java Quiz Online Practice Test

问题 11. What is the purpose of the System class?

The purpose of the System class is to provide access to system resources.

public static void main(String args[])
{
System.out.println("WithoutBook");
}

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问题 12. What is java.io package in Core Java?

Java.io package provides classes for system input and output through data streams, serialization and the file system.

E.g

java.io.BufferedReader

java.io.FileReader

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问题 13. What is data encapsulation?

Encapsulation may be used by creating 'get' and 'set' methods in a class (JAVABEAN) which are used to access the fields of the object. Typically the fields are made private while the get and set methods are public. Encapsulation can be used to validate the data that is to be stored, to do calculations on data that is stored in a field or fields, or for use in introspection (often the case when using javabeans in Struts, for instance). Wrapping of data and function into a single unit is called as data encapsulation. Encapsulation is nothing but wrapping up the data and associated methods into a single unit in such a way that data can be accessed with the help of associated methods. Encapsulation provides data security. It is nothing but data hiding.

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问题 14. What is java.math package in Core Java?

Java.math package provides classes for performing arbitrary-precision integer arithmetic (BigInteger) and arbitrary-precision decimal arithmetic (BigDecimal).

E.g

java.math.BigDecimal

java.math.BigInteger

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问题 15. What's the difference between J2SDK 1.5 and J2SDK 5.0?

There's no difference, Sun Microsystems just re-branded this version.

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