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Details Title: Java Cert - Ch -6 Description: Java.lang Math and String Wrappers Total Flash Cards: 40 Created: 02/19/2006 15:01:10	To study from this set of flash cards, or to create your own your own study flash cards, register HERE. If you are already a registered user, CLICK HERE.
Cards Term what is a string in java? Definition in java string is a 16 bit character. Term why are strings immutable in jav? Definition jvm sets aside a string constants pool. if a similar string is detected its reference to new string points to old string. saving memory Term can some one extendthe string class Definition nope that si to ensure the immutability of strings remains intact. Term what is the difference between the implicit creation of strings and the explicit creation? Definition in implicit creation just one string object is created in the pool . in explicit both an object in the pool and a object not in the pool are created. Term what does the first argumetn in substring method represent? Definition starting point from where you should substring . This should be a zero based string. Term what does the second argument in the substring represent? Definition the second arg is the ending point based on 1 based counting Term what does the trim method in the string class do. Definition the trim method eliminateds any white spaces in the string. Term when would you use StringBuffer instead of String class? Definition when you will be a lot of modifications on strings so that you dont end up with too many string objects in the pool Term what is the difference between String and StringBuffer class. Definition the String class is immutable. All created objects are left in a pool. StringBuffer is mutalbe and objects are not left in any pool Term what is one syntatical sugar you can use due to mutability of StringBuffer. Definition you can say sb.append("xyz").reverse().insert(3,---) it is called method chaining. Term what is the output of StringBuffer sb = new StringBuffer("Hello).insert(4,"---"); Definition Hell---o Term why are string methods synchronized. Definition because they are all acting on the same data. Term how shoulc you read chaining of methods? Definition from left to right . output of one method becomes input of the other methods. Term how come we dont have to use import statement ot get access to String class? Definition all classes in the java.lang package are imported automatically. Term can you create object of java.lang.Math Definition NO the constructor is private. and you cant extend it the class is final. all methods are static. Term what is Math.ceil(-8.9)? Definition it is -8.0 !! -8 is greater than -9. Term can a ceil method take integers can it return integers. Definition NO! ceil method takes doubles and returns doubles. Term what is Math.floor(-9.8)? Definition -10 Term what is the result of calling Math.random()? Definition a double between 0 and .9999 Term what does round() do? Definition adds .5 and truncates Term what does sin() do. Definition commits a sin in radians with a double Term how to convert 90.0 to radians? Definition Math.toRadians(45.0); Term what does sqrt(-1) do Definition returns NaN. Term how do you determine something is positive infinity , neg infinity of nan Definition Float.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, Double.NaN Term How do you check that double is Nan? Definition Double.isNaN(a) Term what is double devided by 0.0 Definition it is NaN Term What is double devided by -0.0 Definition it si Doble.NEGATIVE_INFINITY Term what happens if you devide integers and floats with 0 Definition you get arithemetic exception. Term Which primitive doesnt have a Wrapper class? Definition every primitive has a wrapper class Term What are the types of constructors which wrapper classes tend to have? Definition two constructors one for their respective types and another to take a string and makeit an integer or whatever Term what kind of values will Boolean take. Definition case insensitive string or actual boolean Term can a boolean object be used in a if statement? Definition NO NO NO Term what is the significance of the valueOf method()? Definition it can take two arguments like Integer.valueOf("101011",2) that becomes 43. ie radix allowed. Term How do you get primitive out of Wrapper? Definition (new Integer(42)).shortValue(); Term What is the difference between parseXxx() and valueOf()? Definition both take strings first one returns the primitive second one returns the wrapper. Term What is the difference between most methods in Wrappers and the toString() method. Definition the toString() method is a non static method. Term What is the function of the toXxxString() method. Definition can be used to convert string to Binary, Hex or Octal. Term what does using == with two reference variables mean? Definition it means weather they do point to the same object Term when used with wrapper objects how does the equals method behave? Definition if both the type of the object and its value are the same ti returns true. Term does the StringBuffer class have an equals method. Definition NO. it uses Object equas method which i tink compares references dont knwo