Java API Object

Java 的API（API: Application(应用) Programming(程序) Interface(接口)）

Java API就是JDK中提供给我们使用的类，这些类将底层的代码实现封装了起来，我们不需要关心这些类是如何实现的，只需要知道这些类如何使用即可。

Object类概述

Object类是Java语言中的根类，即所有类的父类。它中描述的所有方法子类都可以使用。所有类在创建对象的时候，最终找的父类就是Object。

equals

equals方法，用于比较两个对象是否相同，它其实就是使用两个对象的内存地址在比较

public class Person {
	private String name;
	private int age;

	public Person() {
		super();
	}

	public Person(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}
}

　　

public class Test {
	  public static void main(String[] args) {
          Person  p1 = new Person("张三",12);
          Person  p2 = new Person("张三",12);
          System.out.println(p1);
          System.out.println(p2);
          System.out.println(p1.equals(p2));
   }

}

　　

String将equals方法重写

public class Test {
	  public static void main(String[] args) {
          String str = "abc";
          String str1 = "abc";
          System.out.println(str.equals(str1));
   }
}

　　

自定义类的重写

public class Person extends Object{
	private String name;
	private int age;

	public Person() {
		super();
	}

	public Person(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}
	//对equals方法重写
	public boolean equals(int age) {
		if(this.age ==age) {
			return true;
		}
		return false;
	}
}

　　

public class Test {
	  public static void main(String[] args) {
          Person  p1 = new Person("张三",12);
          Person  p2 = new Person("张三",12);
          System.out.println(p1);
          System.out.println(p2);
          System.out.println(p1.equals(p2.getAge()));
   }

}

　　

toString

toString方法返回该对象的字符串表示，其实该字符串内容就是对象的类型+@+内存地址值。

public class Person {
	private String name;
	private int age;

	public Person() {
		super();
	}

	public Person(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}
}

　　

public class Test {
	  public static void main(String[] args) {
          Person  p1 = new Person("张三",12);
          Person  p2 = new Person("张三",12);        
          System.out.println(p1.toString());
          System.out.println(p2.toString());
   }

}

　　

在ArrayList和String中toString方法已经重写不再举例

自定义类的重写

public class Person {
	private String name;
	private int age;
	
	public String toString() {
		return "Person [age=" + age + "]";
	}
	public Person() {
		super();
	}

	public Person(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}
}

　　

public class Test {
	  public static void main(String[] args) {
          Person  p1 = new Person("张三",12);
          Person  p2 = new Person("张三",12);        
          System.out.println(p1.toString());
   }

}