CaseInsensitiveString.java

// Broken - violates symmetry! - Pages 36-37
package org.effectivejava.examples.chapter03.item08;

public final class CaseInsensitiveString {
	private final String s;

	public CaseInsensitiveString(String s) {
		if (s == null)
			throw new NullPointerException();
		this.s = s;
	}

	// Broken - violates symmetry!
	@Override
	public boolean equals(Object o) {
		if (o instanceof CaseInsensitiveString)
			return s.equalsIgnoreCase(((CaseInsensitiveString) o).s);
		if (o instanceof String) // One-way interoperability!
			return s.equalsIgnoreCase((String) o);
		return false;
	}

	// This version is correct.
	// @Override public boolean equals(Object o) {
	// return o instanceof CaseInsensitiveString &&
	// ((CaseInsensitiveString) o).s.equalsIgnoreCase(s);
	// }

	public static void main(String[] args) {
		CaseInsensitiveString cis = new CaseInsensitiveString("Polish");
		String s = "polish";
		System.out.println(cis.equals(s) + "  " + s.equals(cis));
	}
}