Multiple tråde med return

public class Foobar implements Callable<String> {
    public String call()  {
              // do things
              // return string
        }
}

ExecutorService es = Executors.newFixedThreadPool(POOL_SIZE);
Future<String>[] task = new Future[N];
for(int i = 0; i < task.length; i++) {
      // submit task:
      task[i] = es.submit(new Foobar());
}
for(int i = 0; i < task.length; i++) {
      // this blocks until task is completed:
    String res = task[i].get();
    // use res
}
es.shutdown();

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class ThreadFun implements Callable<String> {
    private static final String MSG = "It works!";
    private static final int N = 100;
    @Override
    public String call() throws InterruptedException {
        Thread.sleep(1000);
        return MSG;
    }
    private static void test(int poolsize) throws InterruptedException, ExecutionException {
        long t1 = System.currentTimeMillis();
        ExecutorService es = Executors.newFixedThreadPool(poolsize);
        @SuppressWarnings("unchecked")
        Future<String>[] task = new Future[N];
        for(int i = 0; i < task.length; i++) {
            task[i] = es.submit(new ThreadFun());
        }
        for(int i = 0; i < task.length; i++) {
            String res = task[i].get();
            if(!res.equals(MSG)) throw new RuntimeException("Ooops");
        }
        es.shutdown();       
        long t2 = System.currentTimeMillis();
        System.out.printf("Executing %d tasks in %d threads took %.1f seconds\n", N, poolsize, (t2 - t1) / 1000.0);
    }
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        test(1);
        test(10);
        test(100);
    }
}

mport java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class ThreadFun implements Callable<String> {
    private String sv;
    private int iv;
    public ThreadFun(String sv, int iv) {
        this.sv = sv;
        this.iv = iv;
    }
    @Override
    public String call() throws InterruptedException {
        Thread.sleep(10);
        return sv + iv;
    }
    private static final int POOL_SIZE = 10;
    private static final int N = 100;
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        ExecutorService es = Executors.newFixedThreadPool(POOL_SIZE);
        @SuppressWarnings("unchecked")
        Future<String>[] task = new Future[N];
        for(int i = 0; i < task.length; i++) {
            task[i] = es.submit(new ThreadFun("Test", i));
        }
        for(int i = 0; i < task.length; i++) {
            String res = task[i].get();
            if(!res.equals("Test" + i)) throw new RuntimeException("Ooops");
        }
        es.shutdown();     
    }
}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class DB2List {
    public static class T1 {
        private int f1;
        private String f2;
        public T1(int f1, String f2) {
            this.f1 = f1;
            this.f2 = f2;
        }
        public int getF1() {
            return f1;
        }
        public String getF2() {
            return f2;
        }
    }
    private static List<T1> loadData() throws SQLException {
        List<T1> res = new ArrayList<>();
        try(Connection con = DriverManager.getConnection("jdbc:mysql://localhost/Test", "root", "")) {
            try(Statement stmt = con.createStatement()) {
                try(ResultSet rs = stmt.executeQuery("SELECT f1,f2 FROM t1")) {
                    while(rs.next()) {
                        res.add(new T1(rs.getInt("f1"), rs.getString("f2")));
                    }
                }
            }
        }
        return res;
    }
    public static void m1(List<T1> data) {
        for(T1 o : data) {
            if(o.getF1() < 3) {
                System.out.printf("m1: %d %s\n", o.getF1(), o.getF2());
            }
        }
    }
    public static void m2(List<T1> data) {
        for(T1 o : data) {
            if(o.getF1() >= 3) {
                System.out.printf("m2: %d %s\n", o.getF1(), o.getF2());
            }
        }
    }
    public static void main(String[] args) throws SQLException {
        List<T1> data = loadData();
        m1(data);
        m2(data);
    }
}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class DB2List {
    public static class T1 {
        private int f1;
        private String f2;
        public T1(int f1, String f2) {
            this.f1 = f1;
            this.f2 = f2;
        }
        public int getF1() {
            return f1;
        }
        public String getF2() {
            return f2;
        }
        public Object get(String fld) {
            switch(fld) {
                case "f1":
                    return getF1();
                case "f2":
                    return getF2();
                default:
                    throw new RuntimeException("Unknown field T1." + fld);
            }
        }
    }
    private static List<T1> loadData() throws SQLException {
        List<T1> res = new ArrayList<>();
        try(Connection con = DriverManager.getConnection("jdbc:mysql://localhost/Test", "root", "")) {
            try(Statement stmt = con.createStatement()) {
                try(ResultSet rs = stmt.executeQuery("SELECT f1,f2 FROM t1")) {
                    while(rs.next()) {
                        res.add(new T1(rs.getInt("f1"), rs.getString("f2")));
                    }
                }
            }
        }
        return res;
    }
    public static void m1(List<T1> data) {
        for(T1 o : data) {
            if(o.getF1() < 3) {
                System.out.printf("m1: %d %s\n", o.get("f1"), o.get("f2"));
            }
        }
    }
    public static void m2(List<T1> data) {
        for(T1 o : data) {
            if(o.getF1() >= 3) {
                System.out.printf("m2: %d %s\n", o.get("f1"), o.get("f2"));
            }
        }
    }
    public static void main(String[] args) throws SQLException {
        List<T1> data = loadData();
        m1(data);
        m2(data);
    }
}

import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class DB2ListVar {
    public static class TypeUnsafeBean {
        public Object get(String fld) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, IntrospectionException {
            return new PropertyDescriptor(fld, this.getClass()).getReadMethod().invoke(this);
        }
    }
    public static class T1 extends TypeUnsafeBean {
        private int f1;
        private String f2;
        public T1(int f1, String f2) {
            this.f1 = f1;
            this.f2 = f2;
        }
        public void setF1(int f1) {
            this.f1 = f1;
        }
        public int getF1() {
            return f1;
        }
        public String getF2() {
            return f2;
        }
        public void setF2(String f2) {
            this.f2 = f2;
        }
    }
    private static List<T1> loadData() throws SQLException {
        List<T1> res = new ArrayList<>();
        try(Connection con = DriverManager.getConnection("jdbc:mysql://localhost/Test", "root", "")) {
            try(Statement stmt = con.createStatement()) {
                try(ResultSet rs = stmt.executeQuery("SELECT f1,f2 FROM t1")) {
                    while(rs.next()) {
                        res.add(new T1(rs.getInt("f1"), rs.getString("f2")));
                    }
                }
            }
        }
        return res;
    }
    public static void m1(List<T1> data) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, IntrospectionException {
        for(T1 o : data) {
            if(o.getF1() < 3) {
                System.out.printf("m1: %d %s\n", o.get("f1"), o.get("f2"));
            }
        }
    }
    public static void m2(List<T1> data) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, IntrospectionException {
        for(T1 o : data) {
            if(o.getF1() >= 3) {
                System.out.printf("m2: %d %s\n", o.get("f1"), o.get("f2"));
            }
        }
    }
    public static void main(String[] args) throws SQLException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, IntrospectionException {
        List<T1> data = loadData();
        m1(data);
        m2(data);
    }
}