Here is why Java 10 is awesome ;-)

StringPerformerTest.java

import org.junit.Ignore;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class StringPerformerTest {

    private static final Logger log = LoggerFactory.getLogger(StringPerformerTest.class);

    private static final String S1 = "table";
    private static final String S2 = "variable";
    private static final String S3 = "Monkeys MIGHT 'Climb out of my ass'";

    @Test
    public void testBasic() {
        for(int i=0; i<3; i++) {
            final long start = System.nanoTime();
            for(int j=0; j<1_000_000; j++) {
                basic(S1, S2, S3);
            }
            final long run = System.nanoTime() - start;
            log.info("Time was {}ns, {}/s", run/1E6, 1E6/(run/1e9));

        }
    }

    @Test
    public void testStringBuilder() {
        for(int i=0; i<3; i++) {
            final long start = System.nanoTime();
            for(int j=0; j<1_000_000; j++) {
                stringBuilder(S1, S2, S3);
            }
            final long run = System.nanoTime() - start;
            log.info("Time was {}ns, {}/s", run/1E6, 1E6/(run/1e9));

        }
    }

    @Test
    public void testStringBuilderSize() {
        for(int i=0; i<3; i++) {
            final long start = System.nanoTime();
            for(int j=0; j<1_000_000; j++) {
                stringBuilderSize(S1, S2, S3);
            }
            final long run = System.nanoTime() - start;
            log.info("Time was {}ns, {}/s", run/1E6, 1E6/(run/1e9));

        }
    }


    @Ignore
    public static String basic(String s1, String s2, String s3) {
        return "SELECT " + s1 + " FROM " + s2 + " WHERE " + s3;
    }

    @Ignore
    public static String stringBuilder(String s1, String s2, String s3) {
        return new StringBuilder().append("SELECT ").append(s1)
                .append(" FROM ").append(s2).append(" WHERE ")
                .append(s3).toString();
    }

    @Ignore
    public static String stringBuilderSize(String s1, String s2, String s3) {
        int len = 20 + s1.length() + s2.length() + s3.length();
        return new StringBuilder(len).append("SELECT ").append(s1)
                .append(" FROM ").append(s2).append(" WHERE ")
                .append(s3).toString();
    }
}