Question

What I need to do is check a string and this is what I have so far

System.out.print("Please enter a string of 1's and 0s :");
numLine = input.next();

if (numLine.matches("^101$")) {
    System.out.print("A is true");
} else if (numLine.matches("^\\d[01]+101$ ")){
    System.out.print("B is true");
} else {
    System.out.println("no");  
}

The first part of the code the ^101$ works and prints out A is true
for B what I am trying to do is only accept 1s and 0s and return if it ends in 101
and I would like a C to do 101 at the begining and accept as many 1s and 0s
and a D that does 101 anywhere in it even if its 111000101000 or something else

the killer for me is the (“^101$”) syntax and I could use help with that

Answer 1

You don’t need ^ and $ with matches (as I said in my comment). Here’s the way I see it:

B: "[01]+101"
C: "101[01]+"
D: "[01]*101[01]*"

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Recall that X+ means X one or more times and that X* means X zero or more times.

Also (for A), if you want to ‘match’ only "101", you might want to consider simply using equals instead, i.e. numLine.equals("101").