字符串常量演示Demo

public class StringDemo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub

		String str = "abc";
		String str2 = "abc";
		//System.out.println(str==str2);  //true
		//System.out.println(str.equals(str2)); //true

		String str3 = new String("abc");
		String str4 = "abc";
		//System.out.println(str3==str4);  //false
		//System.out.println(str3.equals(str4)); // true

		String str5 = "ab"+"c";
		String str6 = "a"+"bc";
		//System.out.println(str5==str6);  // true
		//System.out.println(str5.equals(str6)); //true

		String str7 = "ab";
		String str8 = str7+"c";
		String str9 = "ab"+"c";

		//System.out.println(str8.equals(str9)); // true
		//System.out.println(str8 == str9); // false  --str8 是运行时的变量，而str9是字符串常量表达式

		String str10 = "abc";
		String str11 = new String("abc");
		String str12 = str11.intern();
		System.out.println(str10 == str11); //false
		System.out.println(str10.equals(str11)); //true
		System.out.println(str11.equals(str12)); //true

	}

}