Java Tutorial/Class Definition/toString

Jakarta Commons toString Builder

import org.apache.rumons.lang.builder.ToStringBuilder;
import org.apache.rumons.lang.builder.ToStringStyle;
public class Main {
  private String id;
  private String firstName;
  private String lastName;
  public Main() {
  }
  public String toString() {
    return new ToStringBuilder(this, ToStringStyle.MULTI_LINE_STYLE).append("id", id).append(
        "firstName", firstName).append("lastName", lastName).toString();
  }
  public static void main(String[] args) {
    Main example = new Main();
    example.id = "1";
    example.firstName = "First Name";
    example.lastName = "Last Name";
    System.out.println("example = " + example);
  }
}

override the toString method in your classes

public class MainClass {
  public static void main(String[] args) {
    Employee emp = new Employee("Martinez", "Anthony");
    System.out.println(emp.toString());
  }
}
class Employee {
  private String lastName;
  private String firstName;
  public Employee(String lastName, String firstName) {
    this.lastName = lastName;
    this.firstName = firstName;
  }
  public String toString() {
    return "Employee[" + this.firstName + " " + this.lastName + "]";
  }
}

Override toString() for Box class.

class Box {
  double width;
  double height;
  double depth;
  Box(double w, double h, double d) {
    width = w;
    height = h;
    depth = d;
  }
  public String toString() {
    return "Dimensions are " + width + " by " + depth + " by " + height + ".";
  }
}
class toStringDemo {
  public static void main(String args[]) {
    Box b = new Box(10, 12, 14);
    String s = "Box b: " + b; // concatenate Box object
    System.out.println(b); // convert Box to string
    System.out.println(s);
  }
}

Reflection based toString() utilities

import java.lang.reflect.Field;
public class Main {
  String hello = "world";
  int i = 42;
  public static void main(String args[]) {
    System.out.println(Util.toString(new MyClass()));
    
    System.out.println(Util.toString(new MyAnotherClass()));
  }
}
class Util {
  public static String toString(Object o) {
    StringBuilder sb = new StringBuilder();
    toString(o, o.getClass(), sb);
    return o.getClass().getName()+ "\n"+sb.toString();
  }
  private static void toString(Object o, Class clazz, StringBuilder sb) {
    Field f[] = clazz.getDeclaredFields();
    for (int i = 0; i < f.length; i++) {
      f[i].setAccessible(true);
      try {
        sb.append(f[i].getName() + "=" + f[i].get(o)+"\n");
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
    if (clazz.getSuperclass() != null)
      toString(o, clazz.getSuperclass(), sb);
  }
}
class MyClass {
  int i = 1;
  private double d = 3.14;
}
class MyAnotherClass extends MyClass{
  int f = 9;
}

Use a generic toString()

import java.lang.reflect.Field;
public class Main {
  public static void main(String args[]) {
    System.out.println(new MyClass().toString());
  }
}
class MyClass {
  String hello = "hi";
  int i = 0;
  public String toString() {
    StringBuilder sb = new StringBuilder();
    Class cls = getClass();
    Field[] f = cls.getDeclaredFields();
    for (int i = 0; i < f.length; i++) {
      f[i].setAccessible(true);
      try {
        sb.append(f[i].getName()+"="+ f[i].get(this)+"\n");
      } catch (Exception e) {
        e.printStackTrace();
      }
    }
    if (cls.getSuperclass().getSuperclass() != null) {
      sb.append("super:"+ super.toString()+"\n");
    }
    return cls.getName()+"\n" + sb.toString();
  }
}

Use Reflection To build toString method

import org.apache.rumons.lang.builder.ReflectionToStringBuilder;
import org.apache.rumons.lang.builder.ToStringStyle;
public class Main {
  private Integer id;
  private String name;
  private String description;
  public static final String KEY = "APP-KEY";
  private transient String secretKey;
  public Main(Integer id, String name, String description, String secretKey) {
    this.id = id;
    this.name = name;
    this.description = description;
    this.secretKey = secretKey;
  }
  public String toString() {
    return ReflectionToStringBuilder.toString(this, ToStringStyle.SIMPLE_STYLE, true, true);
  }
  public static void main(String[] args) {
    Main demo = new Main (1, "A", "B", "C");
    System.out.println("Demo = " + demo);
  }
}