Term
| what is a string in java? |
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Definition
| in java string is a 16 bit character. |
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Term
| why are strings immutable in jav? |
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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 |
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Term
| can some one extendthe string class |
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Definition
| nope that si to ensure the immutability of strings remains intact. |
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Term
| what is the difference between the implicit creation of strings and the explicit creation? |
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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. |
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Term
| what does the first argumetn in substring method represent? |
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Definition
| starting point from where you should substring . This should be a zero based string. |
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Term
| what does the second argument in the substring represent? |
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Definition
| the second arg is the ending point based on 1 based counting |
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Term
| what does the trim method in the string class do. |
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Definition
| the trim method eliminateds any white spaces in the string. |
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Term
| when would you use StringBuffer instead of String class? |
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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 |
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Term
| what is the difference between String and StringBuffer class. |
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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 |
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Term
| what is one syntatical sugar you can use due to mutability of StringBuffer. |
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Definition
| you can say sb.append("xyz").reverse().insert(3,---) it is called method chaining. |
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Term
| what is the output of StringBuffer sb = new StringBuffer("Hello).insert(4,"---"); |
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Definition
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Term
| why are string methods synchronized. |
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Definition
| because they are all acting on the same data. |
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Term
| how shoulc you read chaining of methods? |
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Definition
| from left to right . output of one method becomes input of the other methods. |
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Term
| how come we dont have to use import statement ot get access to String class? |
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Definition
| all classes in the java.lang package are imported automatically. |
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Term
| can you create object of java.lang.Math |
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Definition
| NO the constructor is private. and you cant extend it the class is final. all methods are static. |
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Term
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Definition
| it is -8.0 !! -8 is greater than -9. |
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Term
| can a ceil method take integers can it return integers. |
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Definition
| NO! ceil method takes doubles and returns doubles. |
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Term
| what is Math.floor(-9.8)? |
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Definition
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Term
| what is the result of calling Math.random()? |
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Definition
| a double between 0 and .9999 |
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Term
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Definition
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Term
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Definition
| commits a sin in radians with a double |
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Term
| how to convert 90.0 to radians? |
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Definition
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Term
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Definition
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Term
| how do you determine something is positive infinity , neg infinity of nan |
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Definition
Float.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY,
Double.NaN |
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Term
| How do you check that double is Nan? |
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Definition
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Term
| what is double devided by 0.0 |
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Definition
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Term
| What is double devided by -0.0 |
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Definition
| it si Doble.NEGATIVE_INFINITY |
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Term
| what happens if you devide integers and floats with 0 |
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Definition
| you get arithemetic exception. |
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Term
| Which primitive doesnt have a Wrapper class? |
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Definition
| every primitive has a wrapper class |
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Term
| What are the types of constructors which wrapper classes tend to have? |
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Definition
| two constructors one for their respective types and another to take a string and makeit an integer or whatever |
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Term
| what kind of values will Boolean take. |
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Definition
| case insensitive string or actual boolean |
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Term
| can a boolean object be used in a if statement? |
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Definition
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Term
| what is the significance of the valueOf method()? |
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Definition
it can take two arguments like
Integer.valueOf("101011",2) that becomes 43. ie radix allowed. |
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Term
| How do you get primitive out of Wrapper? |
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Definition
| (new Integer(42)).shortValue(); |
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Term
| What is the difference between parseXxx() and valueOf()? |
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Definition
| both take strings first one returns the primitive second one returns the wrapper. |
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Term
| What is the difference between most methods in Wrappers and the toString() method. |
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Definition
| the toString() method is a non static method. |
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Term
| What is the function of the toXxxString() method. |
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Definition
| can be used to convert string to Binary, Hex or Octal. |
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Term
| what does using == with two reference variables mean? |
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Definition
| it means weather they do point to the same object |
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Term
| when used with wrapper objects how does the equals method behave? |
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Definition
| if both the type of the object and its value are the same ti returns true. |
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Term
| does the StringBuffer class have an equals method. |
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Definition
| NO. it uses Object equas method which i tink compares references dont knwo |
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