String创建对象的个数--西北狼

public class StringDemo {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		/*第一题：String str = new String("abc");创建了几个对象
		第二题： String s="a"+"b"+"c"+"d"创建了几个对象（假设之前串池是空的）
		第三题：StringBuilder sb = new StringBuilder();
		String a = "a";
		String b = "b";
		String c = "c";
		String d = "d";
		String s = a+b+c+d;  这句话创建了几个对象
		第四题：StringBuilder sb = new StringBuilder();
		sb.append("a").append("b").append("c").append("d");这句话创建了几个对象*/
		
		String str = new String("abc");
		String s = "a" + "b" + "c" + "d"; //创建了几个对象（假设之前串池是空的）
		StringBuilder sb = new StringBuilder();
		String a = "a";
		String b = "b";
		String c = "c";
		String d = "d";
		String s2 = a + b + c + d;
		StringBuilder sb2 = new StringBuilder();
		sb2.append("a").append("b").append("c").append("d");
		
		if(str instanceof Object){
			System.out.println("str是对象");
		}else{
			System.out.println("str不是对象");
		}
		System.out.println("-------------------------");
		if(s instanceof Object){
			System.out.println("s是对象");
		}else{
			System.out.println("s不是对象");
		}
		System.out.println("-------------------------");
		if(a instanceof Object){
			System.out.println("a是对象");
		}else{
			System.out.println("a不是对象");
		}
		
		if(sb instanceof Object){
			System.out.println("sb是对象");
		}else{
			System.out.println("sb不是对象");
		}
		
	}

}