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Regular Expressions

L1

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RegEx1.java
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;
import org.pureprogrammer.Utils;

public class RegEx1 {

	public static void main(String[] args) {
		final String s = "Four score and seven years ago...";
		System.out.println(Utils.join("", "Match 1: ", Pattern.compile("s.*e").matcher(s).find()));
		System.out.println(Utils.join("", "Match 2: ", Pattern.compile("\\bs.*e\\b").matcher(s).find()));
		System.out.println(Utils.join("", "Match 3: ", Pattern.compile("s...e").matcher(s).find()));
		System.out.println(Utils.join("", "Match 4: ", Pattern.compile("b.d").matcher(s).find()));

		List<String> subgroups = Utils.findFirst(Pattern.compile("(\\w+)\\s*(\\w+)"), s);
		System.out.println(Utils.join("", "Find First (with subgroups): ", Utils.listToString(subgroups)));
		subgroups = Utils.findFirst(Pattern.compile("bad match"), s);
		System.out.println(Utils.join("", "Find First (bad match): ", Utils.listToString(subgroups)));

		List<String> matches = Utils.findAll(Pattern.compile("\\w+"), s);
		System.out.println(Utils.join("", "Find All: (matches only)", Utils.listToString(matches)));
		matches = Utils.findAll(Pattern.compile("bad match"), s);
		System.out.println(Utils.join("", "Find All (bad match): ", Utils.listToString(matches)));
	}
}
Output
$ javac -Xlint RegEx1.java $ java -ea RegEx1 Match 1: true Match 2: true Match 3: true Match 4: false Find First (with subgroups): ["Four score", "Four", "score"] Find First (bad match): [] Find All: (matches only)["Four", "score", "and", "seven", "years", "ago"] Find All (bad match): []
RegEx2.java
import java.util.regex.Pattern;
import org.pureprogrammer.Utils;

public class RegEx2 {

	public static void main(String[] args) {
		final String s = "Four score and seven years ago...";
		System.out.println(Utils.join("", "Replace First 1: ", Pattern.compile("\\.\\.\\.").matcher(s).replaceFirst("!!!")));
		System.out.println(Utils.join("", "Replace First 2: ", Pattern.compile("\\b...\\b").matcher(s).replaceFirst("???")));
		System.out.println(Utils.join("", "Replace First 3: ", Pattern.compile("b.d").matcher(s).replaceFirst("???")));
		System.out.println(Utils.join("", "Replace First 4: ", Pattern.compile("(\\w+) (\\w+)").matcher(s).replaceFirst("$2 $1")));

		System.out.println(Utils.join("", "Replace All 1: ", Pattern.compile("\\b...\\b").matcher(s).replaceAll("???")));
		System.out.println(Utils.join("", "Replace All 2: ", Pattern.compile("(\\w+) (\\w+)").matcher(s).replaceAll("$2 $1")));
	}
}
Output
$ javac -Xlint RegEx2.java $ java -ea RegEx2 Replace First 1: Four score and seven years ago!!! Replace First 2: Four score ??? seven years ago... Replace First 3: Four score and seven years ago... Replace First 4: score Four and seven years ago... Replace All 1: Four score ??? seven years ???... Replace All 2: score Four seven and ago years...
RegEx3.java
import java.util.Arrays;
import java.util.regex.Pattern;
import org.pureprogrammer.Utils;

public class RegEx3 {

	public static void main(String[] args) {
		final String STR = "Four score and seven years ago...";
		System.out.println(Utils.join("", "Split 1: ", Utils.listToString(Arrays.asList(Pattern.compile(" ").split(STR)))));
		System.out.println(Utils.join("", "Split 2: ", Utils.listToString(Arrays.asList(Pattern.compile("[eo]").split(STR)))));
		System.out.println(Utils.join("", "Split 3: ", Utils.listToString(Arrays.asList(Pattern.compile("\\s").split(STR)))));
		System.out.println(Utils.join("", "Split 4: ", Utils.listToString(Arrays.asList(Pattern.compile("\\W").split(STR)))));
	}
}
Output
$ javac -Xlint RegEx3.java $ java -ea RegEx3 Split 1: ["Four", "score", "and", "seven", "years", "ago..."] Split 2: ["F", "ur sc", "r", " and s", "v", "n y", "ars ag", "..."] Split 3: ["Four", "score", "and", "seven", "years", "ago..."] Split 4: ["Four", "score", "and", "seven", "years", "ago"]
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