java字符串面试题

1.

package com.gavin.convert;

public class Test3 {

	public static void main(String[] args) {
		String str1 = new String("abc");
		StringBuffer buffer = new StringBuffer("abc");
		joinChar(str1);
		appendChar(buffer);
		
		System.out.println(str1);
		System.out.println(buffer);
		
	}
	
	public static void joinChar(String string){
		string = string +'d';
	}
	
	public static void appendChar(StringBuffer buffer){
		buffer = buffer.append('d');
	}

}

结果：

abc
abcd

2.

参考：http://www.360doc.com/content/11/0310/12/3446769_99823666.shtml

package com.gavin.convert;

public class Test4 {

	public static void main(String[] args) {
		String aString = "a1";
		String bString = "a"+1;
		System.out.println(aString == bString);
	}

}

结果：
true

3.

package com.gavin.convert;

public class Test5 {
	public static void main(String[] args) {
		String aString2 = "b1";
		String cString2 = "1";
		String bString2 = "b"+cString2;
		System.out.println(aString2 == bString2);
	}
}

结果：
false

4.

package com.gavin.convert;

public class Test6 {

	public static void main(String[] args) {
		String aString2 = "b1";
		final String cString2 = "1";
		String bString2 = "b"+cString2;
		System.out.println(aString2 == bString2);
		
	}
}

结果：
true

5.

package com.gavin.convert;

public class Test7 {

	public static void main(String[] args) {
		String aString2 = "ab";
		final String cString2 = getB();
		String bString2 = "a"+cString2;
		System.out.println(aString2 == bString2);
		
	}
	
	private static String getB() {
		return "b";
	}

}

结果：
false

6.

package com.gavin.convert;

public class Test8 {
	private static String aString = "ab";
	public static void main(String[] args) {
		String aString2 = "a";
		String bString2 = "b";
		String string = aString2 + bString2;
		System.out.println(aString == string);
		System.out.println(aString == string.intern());
	}
}

结果：
false
true

7.

package com.gavin.convert;

public class Test9 {

	private static String aString = new String("ab");
	public static void main(String[] args) {
		String aString2 = "a";
		String bString2 = "b";
		String string = aString2 + bString2;
		System.out.println(aString == string);
		System.out.println(aString == string.intern());
		System.out.println(aString.intern() == string.intern());
	}

}

结果：

false
false
true

8.String aStr = new String("abc");创建了几个对象？

答案：2个；

9.String aStr = “abc”；创建了几个对象？

答案：1个；

10.String aStr = "abc"; String bStr = "abc";创建了几个对象？

答案：1个；

11.String a = “ab” + "cd";创建了几个对象？

答案：3个；

12.String aString = new String("ab" + "cd");创建了几个对象？

答案：2个；

package com.gavin.convert;

public class Test10 {
	public static void main(String[] args) {
		System.out.println("ab" == ("a" + "b"));
	}
}