JAVA regarding a particular method -
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i got java test paper , there 1 question has been bugging me.
there question:
what output of following program?
public class swap { public static void swap(int[] a){ int temp = a[1]; a[1] = a[0]; a[0] = temp; } public static void main(string[] args){ int[] x = {5,3}; swap(x); system.out.println("x[0]:" + x[0] + " x[1]:" + x[1]); } } the thought first came mind trick question. since swap method return type void, thought had no effect on int[] x array. answer x[0]:5 x[1]:3. got correct answer , when saw had been marked wrong, got confused. went try out actual code on netbeans , realized values in array got swapped! went on test if case string. typed in similar different code:
public class switch { public static void switch(string s){ s = "goodbye"; } public static void main(string[] args){ string x = "hello"; switch(x); system.out.println(x); } } the output still printed hello instead of goodbye. question why method not change string changes values inside array?
in java - "references objects passed value".
public class swap { public static void swap(int[] a){ // = x --> {5,3} int temp = a[1]; a[1] = a[0]; // swapping a[0] , a[1] in , next step. a[0] = temp; // a[] goes out of scope since both x , pointing "same" object {5,3}, changes made reflected in x i.e, in main method. } public static void main(string[] args){ int[] x = {5,3}; // here - x reference points array {5,3} swap(x); system.out.println("x[0]:" + x[0] + " x[1]:" + x[1]); } } and,
public class switch { public static void switch(string s){ // s=x="hello" s = "goodbye"; //here x="hello" , s ="goodbye" i.e, changing "s" point different string i.e, "goodbye", "x" still points "hello" } public static void main(string[] args){ string x = "hello"; switch(x); system.out.println(x); } }
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