Java 类型转换

类型转换

public class CharToIntExample {
	public static void main(String args[]) {
		char c = 'a';
		char c2 = '1';
		int a = c;
		int b = c2;
		System.out.println(a);
		System.out.println(b);
		
		int d=Character.getNumericValue(c2);  
		System.out.println(d);  
	}
}

import java.sql.Timestamp;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateToTimestampExample {
	public static void main(String args[]) {
		Date date = new Date();
		Timestamp ts = new Timestamp(date.getTime());
		System.out.println(ts);
		SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		System.out.println(formatter.format(ts));
	}
}

public class IntToStringExample1 {
	public static void main(String args[]) {
		int i = 200;
		String s = String.format("%d", i);
		System.out.println(s);
	}
}

public class IntToStringExample2 {
	public static void main(String args[]) {
		int i = 200;
		String s = Integer.toString(i);
		System.out.println(i + 100);// 300 because + is binary plus operator
		System.out.println(s + 100);// 200100 because + is string concatenation operator
	}
}

import org.junit.Test;

public class LongToStringExample {
	@Test
	public void test1() {
		long i = 9993939399L;
		String s = String.valueOf(i);
		System.out.println(s);
	}

	@Test
	public void test2() {
		long i = 9993939399L;
		String s = Long.toString(i);
		System.out.println(s);
	}
}

import org.junit.Test;

public class ObjectToStringExample {
	@Test
	public void test() {
		String s = "hello";
		StringBuilder sb = new StringBuilder(s);
		sb.reverse();
		String rev = sb.toString();// converting StringBuilder to String
		System.out.println("String is: " + s);
		System.out.println("Reverse String is: " + rev);
	}
}

import org.junit.Test;

public class StringToFloatExample {
	@Test
	public void test() {
		String s = "23.6";
		float f = Float.parseFloat(s);
		System.out.println(f);
	}
}

public class StringToIntegerExample {
	public static void main(String args[]) {
		String s = "hello";
		int i = Integer.parseInt(s);
		System.out.println(i); // NumberFormatException
	}
}

public class StringToLongExample {
	public static void main(String args[]) {
		String s = "9990449935";
		long l = Long.parseLong(s);
		System.out.println(l);
	}
}

public class TestStringToInt {
	public static void main(String[] args) {
		int a = Integer.parseInt("123");
		Integer integer = Integer.valueOf(123);
		System.out.println(a + 100);
		System.out.println(integer + 100);
	}
}