equals方法

Java equals

equals方法

Object类中定义有:

public boolean equals(Object obj)方法

提供定义对象是否”相等“的逻辑。

Object的equals方法定义为: x.equals(y)当x和y是同一个对象时返回true否则返回false

JDK提供的一些类，如String,Date等，重写了Object的equals方法，调用这些类的equals方法，x.equals(y)，当x和y所引用的对象是同一类对象且属性内容相等时（并不一定是相同对象），返回true否则返回false.

可以根据需要在用户自定义类型中重写equals方法.

(bjsxt)

When doing coursera Algorithem week4 assignment and determining whether two 3-3 boards are equal, I wrote codes like this:

 public boolean equals(Object y){                                              // does this board equal y?
    if (y == this) return true;                                                  //check out Transaction.java and imitate
    if (y == null) return false;
    if (y.getClass() != this.getClass()) return false;
    Board that = (Board) y;
    if(this.dimension() != that.dimension()) {
        return false;
    }
    //return (this.board == that.board) && (this.n == that.n);       this could be reference equal                               
    for(int i = 0; i<n; i++){
        for(int j = 0; j< n; j++) {
            if (this.board[i][j] != that.board[i][j]) {
                return false;
            }
        }
    }
    return true;
  }

This brought me to take a deeper look at the equals method.