How to find a random entered number in a stack -

so i'm doing creating stack , find way search random number in stack. if code is:

    stack thisstack = new stack();       scanner userinput = new scanner(system.in);      = userinput.nextint();       b = userinput.nextint();       c = userinput.nextint();      showpush(thisstack, a);       showpush(thisstack, b);       showpush(thisstack, c); 

my question how find number user inputs, , able throw exception if number isn't there. if stack user inputs [42, 543, 12] , 42 shows 42 if 43 says "number not in stack"

since stack class inherits vector class, have access contains() method.

contains() returns true if object in stack; false if not, 1 trivial implementation of showpush() method be:

void showpush(stack stack, int num){     if (stack.contains(num)){         system.out.println(num);     } else {         system.out.println("number not in stack");     } } 

where num search target, , stack... stack.

one thing note here when declaring stack (since generic type) have declare type arguments (to ensure type safety), bears following change in thisstack's declaration:

stack<integer> thisstack = new stack<integer>();

you can check mureinik's answer here.

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edit/appendix

just completeness, have added small demo 2 different types of user input (int , float) being pushed stack. possible when declaring stack more general <object> type argument, follows:

import java.util.stack; import java.util.scanner;  public class jst {     void showpush(stack stack, object obj){         if (stack.contains(obj)){             system.out.println("found "+obj+" in stack");         } else {             system.out.println(obj+" not in stack");         }     }      public static void main(string[] arguments){         jst j = new jst(); //either way or declare showpush static         stack<object> thisstack = new stack<object>();          scanner userinput = new scanner(system.in);         int a,pb;         float b,pa;          // user input         system.out.print("enter 2 numbers (int, float):");         try {             = userinput.nextint();               b = userinput.nextfloat();         } catch (exception e) {             system.out.println("exception : "+e.tostring());             return;         }          // push user input stack         system.out.print("\npushing user input stack...");         thisstack.push(a);         thisstack.push(b);         // check stack         system.out.println("checking stack...");         j.showpush(thisstack, a);           j.showpush(thisstack, b);          // pop stack contents         system.out.print("\npopping stack contents...");         pa = (float)thisstack.pop();         pb = (int)thisstack.pop();         system.out.println("popped contents : [ "+pa+", "+pb+" ] (notice stack lifo)");         // check stack         system.out.println("checking stack...");         j.showpush(thisstack, a);           j.showpush(thisstack, b);            // push b in stack         system.out.print("\npushing "+b+" stack...");         thisstack.push(b);         // check stack         system.out.println("checking stack...");         j.showpush(thisstack, a);           j.showpush(thisstack, b);     } } 

which yields:

c:\>java jst enter 2 numbers (int, float):1 23.4  pushing user input stack... checking stack... found 1 in stack found 23.4 in stack  popping stack contents... popped contents : [ 23.4, 1 ] (notice stack lifo) checking stack... 1 not in stack 23.4 not in stack  pushing 23.4 stack... checking stack... 1 not in stack found 23.4 in stack