MemoryLimit.java

import java.io.IOException;
import java.io.InputStream;

import static java.lang.Thread.sleep;

public class MemoryLimit {
    private static final int TRY_COUNT = 5;
    public static void main(String[] args) throws IOException, InterruptedException {
        double memory = 10_000_000;
        double lastSuccessMemory = memory;
        double lastFailedMemory;
        while(true) {
            int mem = (int) memory;

            boolean succeed = tryProcess(
                    "java",
                    "-Xmx" + mem,
                    "-jar",
                    "./build/libs/demo-0.0.1-SNAPSHOT.jar");
            System.out.format("% 10d\t%b\n", mem, succeed);

            if (succeed) {
                lastSuccessMemory = memory;
                memory = memory * 0.95;
            } else {
                lastFailedMemory = memory;
                break;
            }
        }
        double startMem = (lastSuccessMemory + lastFailedMemory) / 2;
        System.out.println("center=" + startMem);
        double div = 0.01;
        boolean upper = true;

        for (int j = 0;j < 10;j++) {
            int mem = (int)startMem;
            int success = 0;
            System.out.format("% 10d ", mem);
            for (int i = 0;i < TRY_COUNT;i++) {
                boolean succeed = tryProcess(
                        "java",
                        "-Xmx" + mem,
                        "-jar",
                        "./build/libs/demo-0.0.1-SNAPSHOT.jar");
                System.out.format(" %b", succeed);

                if (succeed) {
                    success++;
                }
            }
            int successRate = (success * 100 / TRY_COUNT);
            System.out.println(" success rate = " + successRate + "% div=" + div + " upper=" + upper);
            if (successRate < 50) {
                startMem = startMem * (1 + div);
                if (!upper) {
                    div = div / 2;
                }
                upper = true;
            } else {
                startMem = startMem * (1 - div);
                if (upper) {
                    div = div / 2;
                }
                upper = false;
            }
        }

    }

    private static boolean tryProcess(String... args) throws IOException, InterruptedException {
        final Process process = new
                ProcessBuilder(args).start();

        boolean succeed = false;
        InputStream inputStream = process.getInputStream();
        byte[] buff = new byte[10000];
        for (int i = 0;i < 100 && process.isAlive();i++) {
            if (inputStream.available() > 0) {
                int len = inputStream.read(buff);
                String line = new String(buff, 0, len);

//                    System.out.print(line);
                if (line.contains("Tomcat started on port")) {
                    succeed = true;
                    break;
                }
            }
            sleep(100);
        }
        process.destroy();
        return succeed;
    }
}