JAva,Stringパラメータの実パラメータ値は変わらず,equalsと==浅析

1643 ワード

public class Test {

	public static void test(String str) {
		str = "World";
	}///       str    ,   string   ,         (  )

	public static void main(String[] args) {

		String string = "Hello";
		test(string);
		System.out.println(string);hello

		String s = "abc";
		String t = "a";
		String u = s.substring(0, 1);
		// System.out.println(s.substring(0, 1));
		System.out.println(t.equals(s.substring(0, 1))); // //True
		System.out.println(t == s.substring(0, 1));// /false
		System.out.println(t.equals(u)); //True
		System.out.println(t == u); //false
		System.out.println(u.equals(s.substring(0, 1))); // //True
		System.out.println(u == s.substring(0, 1));// /false //s.substring(0, 1);          String  
		System.out.println(s.substring(0, 1).equals(s.substring(0, 1)));///true
		System.out.println(s.substring(0, 1) == s.substring(0, 1));///false
		
		Test t1 = new Test();///t1  Test  1
		Test t2  = new Test();//t2  Test  2
		
		System.out.println(t1.equals(t2)); //false
		System.out.println(t1 == t2); //false
		Test t3 = t1;//t1 t3   Test  1   
		System.out.println(t1.equals(t3)); //true ///                
		System.out.println(t1 == t3); //true
		System.out.println(t2.equals(t3)); //false
		System.out.println(t2 == t3); //false
		
//		 JAVA           Object     , Object          equals   ,
//		                     ,                 ,
//		  String,Integer,Date      equals       ,                  
		
//		==                  
//		equals(),		String,Integer,Date     ,         ;                 
		
		
	}
}
Stringについて  str 3="abc".....のequals(),==比較的簡単すぎて書かない