Which is better Which is better Assume s1 and s2 are Strings A if s1 s2 B if s1 equals s2 Answer B s1 s2 tests whether s1 and s2 reference the same string s1 equals s2 tests whether they reference equal strings String s1 ABC String s2 s1 String s3 ABC String s4 AB C All these strings are equal but s4 is in a different memory location than the others so the test yields false Which is better Assume String s1 A if s1 equals OK B if OK equals s1 Answer B s1 equals OK sends a message to s1 asking if it is equal to OK OK equals s1 sends a message to OK asking if it is equal to s1 This is legal because OK is a String If s1 is null then s1 equals OK gives a NullPointerException OK equals s1 gives false Which is better Assume int numbers new int 100 A for int i 0 i 100 i numbers i i B for int i 0 i 99 i numbers i i Answer A for int i 0 i 100 i is better than for int i 0 i 99 i Three reasons The first is more traditional The array size is 100 not 99 so it s more obvious where the number came from You have to do some arithmetic to get 99 If you change the array size a search for 100 won t find the loop that uses 99 Which is better Assume int numbers new int 100 A for int i 0 i 100 i numbers i i B for int i 0 i numbers length i numbers i i Answer B for int i 0 i numbers length i is better than for int i 0 i 100 i If you later decide to change the size of the numbers array you only need to do it in the declaration the for loop that uses length will automatically adjust Which is better Assume finished is a boolean variable A if finished true B if finished Answer B finished true is redundant If finished is true then finished true will be true If finished is false then finished true will be false The extra words don t gain you anything finished true might seem more readable to a beginner but you quickly learn to read the shorter form Brevity in programming as in writing is a virtue You can avoid the possible mistake of saying if finished true Which is better Assume foo bar and larger are integers A if foo bar larger foo else larger bar B larger foo bar foo bar Answer neither For each of these you have to look at the code carefully to make sure it is correct larger Math max foo bar is easier to read and more obviously correct Which is better A String s Hello B String s new String Hello Answer A Hello is special syntax to implicitly construct a string String s new String Hello actually constructs two strings Hello constructs the first string then it is given as a parameter to an explicit constructor which constructs the second string Which is better Suppose p is a Panel with a BorderLayout and okButton is a Button A p add okButton BorderLayout NORTH B p add okButton North Note BorderLayout NORTH North Answer A p add okButton BorderLayout NORTH is strongly recommended over the shorter form p add okButton North but why Answer better error detection If you type p add okButton north there is no error but it doesn t do what you want If you type p add okButton BorderLayout North you will get a syntax error because BorderLayout has no such variable as North Which is better Suppose n is an int and s is a String A s Integer toString n B s String valueOf n C s new Integer n toString D s n Answer D I prefer D s n because It s a common idiom therefore easily recognized It s short It works for any type Which is better Assume n is an integer A if n 0 n 0 B if n 0 n 0 C if n 0 n 0 Answer C If later on you want to add a statement it s easy to make this mistake with B if n 0 System out println n was n n 0 You won t make this mistake with A or C With C using braces you don t have to change anything that s already there However A all on one line is often convenient Which is better Assume n is an integer A int factorial 1 for int i 2 i n i factorial n B int factorial 1 int i 1 for i 2 i n i factorial n Answer A In most cases you don t care about the index of a for loop outside the loop You typically give it an initial value in the loop You typically already have its final value in some variable or by some simple computation If you don t need a variable you shouldn t have that variable It doesn t help anything and it might get in the way Conclusions There are various ways to do things One way may be better than another because It s easier to read and understand It s more familiar the way things are usually done It s less error prone or provides better error detection It s more efficient The End
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